Router device, datagram transfer method and communication system realizing handoff control for mobile terminals

ABSTRACT

A mobile supporting router device for realizing the handoff control associated with the moving in high speed is forms by at least one first interface connected with radio base stations, each capable of accommodating at least one mobile terminal; at least one second interface connected with a wire network; an information exchanging unit for exchanging a routing protocol on a network layer, through the second interface; a memory unit for storing information regarding a routing on the network layer based on the routing protocol exchanged by the information exchanging unit; a transfer unit for transferring datagram through the first interface according to the information regarding the routing on the network layer stored in the memory unit; a moving detection unit for detecting a moving of the mobile terminal among the radio base stations; and an information updating unit for updating the information regarding the routing on the network layer stored in the memory unit when the moving of the mobile terminal is detected by the moving detection unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a router device to be connected toInternet accommodating mobile terminals, and a datagram transfer methodand a communication system using such a router device.

2. Description of the Background Art

The router device is used in connecting LANs (Local Area Networks) andplays a role of transferring datagram from one LAN to another LAN.Datagram contains communication information data to be transferred aswell as a description of its source and destination network layeraddress (such as IP addresses in the case of IP), and the router devicedetermines an output interface (port number) and a next transfer targetnode (router device or host functioning as communication terminal) ofthe datagram according to such an address information contained in thedatagram.

Now, the routing by the router device in a network will be described foran exemplary case of transmitting an IP packet from a terminal A to aterminal B. In this case, the IP packet transmitted from the terminal Ais routed through Internet according to its IP address and transmittedup to a subnet to which the terminal B belongs. Here, the IP packettransmitted from the terminal A is applied with the IP forwardingprocessing in a form of: datalink layer→IP packet→processing of IPheader information and the like and output target determination→datalinklayer packet, whenever the IP packet passes through a router devicewithin Internet. Once the IP packet reaches to a router device in afinal subnet, the logical-physical address conversion is carried out byARP (Address Resolution Protocol) (by which the MAC address is obtainedfrom the IP address), and the IP packet is transmitted to the terminal Bafter being converted into a datalink layer packet by attaching adatalink layer header information such as this MAC address.

Note here that, at a time of transferring datagram, the conventionalrouter device realizes the processing up to the datalink layer (layer 2)by hardware and the processing of the network layer (such as IPforwarding processing, for example) by software.

However, such a conventional router device has been associated with aproblem that the throughput of the software processing on the networklayer is low compared with the fast hardware processing up to thedatalink layer and causes a bottleneck so that the advantage of the fasthardware processing cannot be taken fully.

In order to resolve this problem, currently there are intensive researchand development activities on a “high speed router device” for realizingthe fast IP packet transfer.

The high speed router device can shorten the “delay time” since thepacket is entered until it is outputted by using the hardware processingrather than the software processing for the packet transfer, and therebyrealize as much faster transfer processing. The usual delay time due tothe packet transfer processing by software is several milli-seconds,whereas the delay time of the packet transfer processing by hardware isabout 100 micro-seconds, so that approximately ten times faster packettransfer can be realized.

There are two propositions for such a high speed router device,including the cut-through scheme and the hop-by-hop scheme.

(1) High speed router device in Cut-through scheme:

The cut-through scheme is a scheme in which the transfer processing ishandled by a layer 2 switch on a lower level layer. Prior to thecut-through, the layer 2 information such as MAC address is exchanged bya specific protocol between terminals or router devices. Then, therouter device realizes the transfer by setting up a cut-through path forby-passing through the layer 2 switch without bringing the processing upto the network layer (layer 3).

(2) High speed router device in Hop-by-hop scheme:

The hop-by-hop scheme is a scheme in which no exchange by a specificprotocol as in the cut-through is required and the same processing asapplied in the general router is applied to every input packet withinthe high speed router device. It differs from the general router in thatthe processing is done by the special hardware chip. The packet transferprocessing to be carried out by the router goes through the processessuch as CRC check of a frame, reading of a destination IP address withinan IP packet, filtering processing, searching through a routing table,and replacement of MAC address, and the same processing is to be carriedout every time except for the processing such as filtering. By utilizingthe hardware processing or cache processing in such a portion of theprocessing which is to be carried out every time, it is possible torealize the fast transfer processing.

There is also a scheme in which the processing delay is suppressed byomitting the routing processing itself rather than utilizing hardwarefor the routing processing. Namely, in this scheme, an external switchnode is provided in addition to the conventional router device, and thisswitch node has an ARP table in which IP addresses and MAC addresses ofterminals moving over plural subnets are set in correspondence. When apacket destined to another subnet is entered from one subnet, thispacket is directly sent to the destination terminal by looking up theARP table. In this scheme, however, only the communications betweensubnets which are directly connected to the switch node are possible andthe transfer processing for a subnet which is not directly connectedcannot be done because there is no routing processing, so that there isa need to use the switch node and the usual router simultaneously.

Thus, currently there are intensive research and development activitieson a “high speed router device” for realizing the fast IP packettransfer by resolving the bottleneck of the network layer processing inthe router device. On the other hand, there are also research anddevelopment activities for a technique to accommodate mobile terminalsin Internet type network. Such a mobile access technique includes ascheme using DHCP (Dynamical Host Configuration Protocol) server and ascheme using Mobile IP.

The scheme using DHCP server is a scheme in which the mobile terminalmakes an Internet access by temporarily obtaining an IP address from theDHCP server within the network. The problem associated with this schemeusing DHCP server is that the strategy to utilize the IP addressdynamically obtained from the network of the visited site works well inthe case where the mobile terminal makes an access to a server in aninternal network, that is, the case where the mobile terminal is a calloriginating side, but it does not work well in applications where themobile terminal can be a call terminating side such as Internettelephone and electronic conference system. Namely, in suchapplications, it is difficult for the other machines to ascertain the IPaddress currently used by the mobile terminal so that it is practicallyimpossible to make an access to the mobile terminal from the othermachines.

The Mobile IP is a scheme developed in order to resolve such a problem.This is a technique to make the mobile terminal appear as if it islocated at its normal location with respect to the other machinesregardless of its actual location on the network. This scheme has beenput in the stage of RFC (Request For Comments) by the IETF (InternetEngineering Task Force) in October, 1996.

The operation of the Mobile IP will now be described with reference toFIG. 1. First, a home agent (HA: 10.1) is provided in advance at anetwork to which the mobile terminal (MH: 10.2) is normally connected.Then, when the mobile terminal (MH: 10.2) moves and is connected to avisited site network (FA: 20.1), it notifies the IP address (FA: 20.1)of the current location to the home agent (HA: 10.1). Thereafter, thehome agent transfers an IP packet in which the IP address (MH: 10.2) ofthe normal location of the mobile terminal is specified as a destinationto the current location of the mobile terminal by encapsulating that IPpacket.

In the case of returning a message from the current location to anaccess source, an IP packet is outputted directly to the access sourcewithout using the home agent. In this manner, it becomes possible foreach node on the network to make an access to the mobile terminal byusing the home address of the mobile terminal regardless of where themobile terminal is currently connected to.

The Mobile IP has been designed with an aim of requiring as littlechange in the existing Internet as possible so that it has a highaffinity with the existing Internet but it is also associated with thefollowing problems.

The first problem is that HA must always relay packets to MH.Consequently, even when HA is located very far away, it is necessary totransfer packets via HA and therefore there is a redundancy in thetransfer route and the delay time of communication will inevitablyincreases.

The second problem is that packets destined to MH cannot be relayed bythe usual routing control because the IP address of HA is held as it iseven at a visited site and therefore there is an IP address in violationof the subnet model.

The third problem is that it is impossible to carry out the processingof a relay router with respect to a header of an original IP packetbecause a packet is transferred in an encapsulated form.

The fourth problem is that all communications with MH become impossiblewhen HA malfunctions, because all communications must go through HA.

Among these problems, the first problem in particular is problematic inrealizing real time communications even in Internet type network. Forinstance, an exemplary case shown in FIG. 2 has not only a considerableroute redundancy but also a further delay time increase due to thebottleneck of the software processing because of the use of routers withconventional software processing, compared with the ideal case shown inFIG. 4.

For this reason, when the cut-through transfer is carried out by usingthe above described high speed router device, the transfer route becomesas shown in FIG. 3, and it can be expected that the delay time isconsiderably shortened compared with the case of FIG. 2. however, evenwhen the Mobile IP technique and the high speed router device are usedtogether, the problem of transfer route redundancy remains unresolved,and the delay time is still considerably large compared with the idealcase of FIG. 4.

Moreover, the Mobile IP scheme is a technique for accesses to/frommobile terminals in Internet type network and its goal is to enableInternet access from any visited site. For this reason, the Mobile IPscheme does not sufficiently account for the case of communicationduring moving, and adopts a method for making a re-connection when thecommunication is disconnected suddenly at a visited site. As a result,it requires a considerable amount of time in the handoff controlassociated with the moving, and it is difficult to realize the real timecommunications while moving as realized in the telecommunication typemobile communication system by the currently available technique.Consequently, there is a problem that it is difficult to realize thereal time communications like Internet telephone under the mobileInternet environment.

Furthermore, the conventional mobile access technique such as the MobileIP scheme, the mobility is supported by the routing at the network layerlevel so that the IP forwarding processing must be executed at a routerdevice, and there is a problem that the router can be a bottleneck inthe case where many mobile terminals coexist within a subnet of somerouter.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a routerdevice to be connected to Internet accommodating mobile terminals, whichis capable of realizing the handoff control associated with the movingin high speed.

It is another object of the present invention to provide a router deviceto be connected to Internet accommodating mobile terminals, which iscapable of switching a transfer target at the datalink level andrealizing a transfer through an optimum route at a visited site even inthe case of transfer over plural radio base stations, by ascertainingthe visited site according to a location information using a functionfor managing local location moving of mobile terminals.

It is another object of the present invention to provide a datagramtransfer method and a communication system using such a router device.

According to one aspect of the present invention there is provided arouter device, comprising: at least one first interface connected with aplurality of radio base stations, each radio base station being capableof accommodating at least one mobile terminal; at least one secondinterface connected with a network; an information exchanging unit forexchanging a routing protocol on a network layer, through the secondinterface; a memory unit for storing information regarding a routing onthe network layer based on the routing protocol exchanged by theinformation exchanging unit; a transfer unit for transferring datagramthrough the first interface according to the information regarding therouting on the network layer stored in the memory unit; a movingdetection unit for detecting a moving of the mobile terminal among theradio base stations; and an information updating unit for updating theinformation regarding the routing on the network layer stored in thememory unit when the moving of the mobile terminal is detected by themoving detection unit.

According to another aspect of the present invention there is provided arouter device, comprising: at least one first interface connected with aplurality of radio base stations, each radio base station being capableof accommodating at least one mobile terminal; at least one secondinterface connected with a network; an information exchanging unit forexchanging a routing protocol on a network layer, through the secondinterface; a memory unit for storing information regarding a routing onthe network layer based on the routing protocol exchanged by theinformation exchanging unit; a transfer unit for transferring datagramthrough the first interface according to another information regarding aswitching on a lower layer of the network layer for enabling datagramtransfer along the routing on the network layer; a moving detection unitfor detecting a moving of the mobile terminal among the radio basestations; and an information updating unit for updating the informationregarding the routing on the network layer stored in the memory unitwhen the moving of the mobile terminal is detected by the movingdetection unit.

According to another aspect of the present invention there is provided arouter device, comprising: a memory unit for storing informationregarding a routing on a network layer; a transfer unit for transferringdatagram to a mobile terminal accommodated in a radio base station towhich the router device is connected, according to the informationregarding the routing on the network layer; an address allocation unitfor allocating a network layer address to the mobile terminal locatedwithin an area managed by the router device; a moving detection unit fordetecting a moving of the mobile terminal out from the area managed bythe router device; an updating unit for updating the informationregarding the routing on the network layer when the moving is detectedby the moving detection unit; and an address release unit for releasingthe network layer address when the moving is detected by the movingdetection unit.

According to another aspect of the present invention there is provided adatagram transfer method, comprising the steps of: storing a mobileterminal identifier uniquely assigned to a mobile terminal, a networklayer address allocated to the mobile terminal, and a correspondencebetween the network layer address allocated to the mobile terminal and avirtual connection to which datagram destined to the network layeraddress should be transmitted; receiving a handoff request containingthe mobile terminal identifier and a base station identifier of a radiobase station of a visited site of the mobile terminal, indicating amoving of the mobile terminal between radio base stations; acquiring avirtual connection to the radio base station of the visited site of themobile terminal indicated by the handoff request, and obtaining thenetwork layer address corresponding to the mobile terminal indicated bythe handoff request according to the first correspondence; updating thecorrespondence so as to set the obtained network layer address incorrespondence to the acquired virtual connection; transmitting a radiochannel allocation request containing the mobile terminal identifier ofthe mobile terminal and a virtual connection identifier of the acquiredvirtual connection, to the radio base station of the visited site of themobile terminal; and transferring datagram according to the updatedcorrespondence or information regarding a switching on a lower layer ofa network layer for enabling datagram transfer according to the updatedcorrespondence, upon receiving the datagram.

According to another aspect of the present invention there is provided acommunication system, comprising: at least one mobile terminal; aplurality of radio base stations; and at least one router device having:a memory unit for storing a first correspondence between a mobileterminal identifier uniquely assigned to the mobile terminal and anetwork layer address allocated to the mobile terminal, and a secondcorrespondence between the network layer address and a virtualconnection to which datagram destined to the network layer addressshould be transmitted; a reception unit for receiving a handoff requestcontaining the mobile terminal identifier and a base station identifierof a radio base station of a visited site of the mobile terminal,indicating a moving of the mobile terminal between radio base stations;an updating unit for acquiring a virtual connection to the radio basestation of the visited site of the mobile terminal indicated by thehandoff request, obtaining the network layer address corresponding tothe mobile terminal indicated by the handoff request according to thefirst correspondence, and updating the second correspondence so as toset the obtained network layer address in correspondence to the acquiredvirtual connection; and a transmission unit for transmitting a radiochannel allocation request containing the mobile terminal identifier ofthe mobile terminal and a virtual connection identifier of the acquiredvirtual connection, to the radio base station of the visited site of themobile terminal; wherein the radio base station of the visited site ofthe mobile terminal has: a memory unit for storing a thirdcorrespondence between a virtual connection from the router device and aradio channel to which datagram received through the virtual connectionfrom the router device should be transmitted; and a setting unit forreceiving the radio channel allocation request from the router deviceand setting a correspondence between a radio channel for the mobileterminal indicated by the radio channel allocation request and theacquired virtual connection indicated by the radio channel allocationrequest as the third correspondence.

According to another aspect of the present invention there is provided acommunication system, comprising: at least one mobile terminal; aplurality of radio base stations; at least one router device having: amemory unit for storing information regarding a routing on a networklayer; a transfer unit for transferring datagram to a mobile terminalaccommodated in a radio base station with which the router device isconnected, according to the information regarding the routing on thenetwork layer; an inter-router moving detection unit for detecting aninter-router moving of the mobile terminal between the router device andanother router device; and an updating unit for updating the informationregarding the routing on the network layer when the inter-router movingis detected by the inter-router moving detection unit; and an addressallocation module having: an inter-network moving detection unit fordetecting an inter-network moving of the mobile terminal betweennetworks corresponding to prescribed network layer address allocationranges; a release unit for releasing a network layer address allocatedto the mobile terminal when the inter-network moving is detected by theinter-network moving detection unit and the address allocation module islocated at an originally located site of the mobile terminal; and anallocation unit for allocating a new network layer address to the mobileterminal when the inter-network moving is detected by the inter-networkmoving detection unit and the address allocation module is located at avisited site of the mobile terminal.

According to another aspect of the present invention there is provided acommunication system, comprising: at least one mobile terminal; aplurality of radio base stations; at least one router device having: amemory unit for storing information regarding a routing on a networklayer; a datagram transfer unit for transferring datagram to a mobileterminal accommodated in a radio base station to which the router deviceis connected, according to the information regarding the routing on thenetwork layer; an inter-base station moving detection unit for detectingan inter-base station moving of the mobile terminal among the radio basestations; and an updating unit for updating the information regardingthe routing on the network layer when the inter-base station moving isdetected by the inter-base station moving detection unit; and a terminallocation management module having: an inter-router moving detection unitfor detecting an inter-router moving of the mobile terminal betweenrouter devices; and an encapsulated datagram transfer unit forencapsulating datagram destined to the mobile terminal using an addressof a network to which a router device or a radio base station of avisited site of the mobile terminal belongs, and transferringencapsulated datagram to the router device of the visited site of themobile terminal.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining a conventional mobile accesstechnique called Mobile IP.

FIG. 2 is a diagram showing a transfer router in the case of using aconventional technique in a form of (Mobile IP+router device).

FIG. 3 is a diagram showing one exemplary transfer router in the case ofusing a conventional technique in a form of (Mobile IP+high speed routerdevice).

FIG. 4 is a diagram showing another exemplary transfer router in thecase of using a conventional technique in a form of (Mobile IP+highspeed router device).

FIG. 5 is a block diagram showing an overall configuration of a mobilecommunication system according to one embodiment of the presentinvention.

FIG. 6 is a diagram showing a functional channel configuration used inthe mobile communication system of FIG. 5.

FIG. 7 is a diagram showing exemplary channel settings among a mobileterminal, a radio base station, and an MSR in the mobile communicationsystem of FIG. 5.

FIG. 8 is a diagram showing exemplary channels to be used among a mobileterminal, a radio base station, and an MSR in the mobile communicationsystem of FIG. 5.

FIG. 9 is a block diagram showing a management function configuration inthe mobile communication system of FIG. 5.

FIGS. 10A and 10B are diagrams showing exemplary charging methods thatcan be used in the mobile communication system of FIG. 5.

FIG. 11 is a diagrams showing another exemplary charging method that canbe used in the mobile communication system of FIG. 5.

FIG. 12 is a diagram showing one exemplary table updating operation at atime of handoff control operation in the mobile communication system ofFIG. 5.

FIG. 13 is a diagram showing another exemplary table updating operationat a time of handoff control operation in the mobile communicationsystem of FIG. 5.

FIG. 14 is a diagram showing still another exemplary table updatingoperation at a time of handoff control operation in the mobilecommunication system of FIG. 5.

FIG. 15 is a diagram showing exemplary connections between MSR and radiobase station in the mobile communication system of FIG. 5.

FIG. 16 is a table showing exemplary base station identifier andterminal identifier that can be used in the mobile communication systemof FIG. 5.

FIG. 17 is a diagram showing one exemplary operation procedure of amobile terminal in the mobile communication system of FIG. 5.

FIG. 18 is a diagram showing another exemplary operation procedure of amobile terminal in the mobile communication system of FIG. 5.

FIG. 19 is a diagram showing an operation state transition of a mobileterminal in the mobile communication system of FIG. 5.

FIG. 20 is a flow chart showing an operation of a mobile terminal at atime of power ON/standby in the mobile communication system of FIG. 5.

FIG. 21 is a sequence chart showing a location registration operationprocedure in the mobile communication system of FIG. 5.

FIG. 22 is a sequence chart showing one exemplary call originationoperation procedure in the mobile communication system of FIG. 5.

FIG. 23 is a sequence chart showing another exemplary call originationoperation procedure in the mobile communication system of FIG. 5.

FIG. 24 is a sequence chart showing one exemplary handoff controlprocedure in the mobile communication system of FIG. 5.

FIG. 25 is a sequence chart showing another exemplary handoff controlprocedure in the mobile communication system of FIG. 5.

FIG. 26 is a diagram showing multicast transfer methods at a time ofhandoff that can be used in the mobile communication system of FIG. 5.

FIG. 27 is a diagram showing one exemplary operation at a time ofhandoff control in the mobile communication system of FIG. 5.

FIG. 28 is a diagram showing another exemplary operation at a time ofhandoff control in the mobile communication system of FIG. 5.

FIG. 29 is a diagram showing another exemplary operation at a time ofhandoff control in the mobile communication system of FIG. 5.

FIG. 30 is a table showing an exemplary configuration of an IP routingtable used in the mobile communication system of FIG. 5.

FIG. 31 is a diagram showing an exemplary configuration of an addressallocation memory unit used in the mobile communication system of FIG.5.

FIG. 32 is a diagram showing exemplary configuration and updatingoperation of a location information memory unit that can be used in themobile communication system of FIG. 5.

FIG. 33 is a diagram showing other exemplary configurations of alocation information memory unit that can be used in the mobilecommunication system of FIG. 5.

FIG. 34 is a diagram showing other exemplary configurations of anaddress allocation memory unit that can be used in the mobilecommunication system of FIG. 5.

FIG. 35 is a diagram showing exemplary configurations of a VPI/VCIconversion table (and a VPI/VCI management table of MSR) that can beused in the mobile communication system of FIG. 5.

FIGS. 36A and 36B are sequence charts showing exemplary communicationdisconnection procedures that can be used in the mobile communicationsystem of FIG. 5.

FIG. 37 is a sequence chart showing one exemplary call terminationconnection operation in the mobile communication system of FIG. 5.

FIG. 38 is a sequence chart showing another exemplary call terminationconnection operation in the mobile communication system of FIG. 5.

FIG. 39 is a block diagram showing an exemplary detailed configurationof an MSR in the mobile communication system of FIG. 5.

FIG. 40 is a table showing an exemplary configuration of a transfertarget memory unit (VPI/VCI management table) used in the MSR of FIG.39.

FIG. 41 is a block diagram showing an exemplary configuration of a radiobase station in the mobile communication system of FIG. 5.

FIG. 42 is a block diagram showing one exemplary internal configurationof a transmission path interface in the radio base station of FIG. 41.

FIG. 43 is a block diagram showing another exemplary internalconfiguration of a transmission path interface in the radio base stationof FIG. 41.

FIG. 44 is a block diagram showing still another exemplary internalconfiguration of a transmission path interface in the radio base stationof FIG. 41.

FIG. 45 is a block diagram showing an exemplary interface configurationamong a channel processing unit, a transmission path interface, and aradio base station control unit in the radio base station of FIG. 41.

FIG. 46 is a diagram showing one exemplary functional arrangement thatcan be used in the mobile communication system of FIG. 5.

FIG. 47 is a diagram showing one exemplary handoff control operation inthe mobile communication system of FIG. 5.

FIG. 48 is a diagram showing another exemplary handoff control operationin the case of moving over router devices in the mobile communicationsystem of FIG. 5.

FIG. 49 is a diagram showing another exemplary functional arrangementthat can be used in the mobile communication system of FIG. 5.

FIG. 50 is a diagram showing another exemplary handoff control operationin the mobile communication system of FIG. 5.

FIG. 51 is a sequence chart showing one exemplary call terminationoperation by Mobile IP in the mobile communication system of FIG. 5.

FIGS. 52A to 52H are sequence charts showing exemplary procedures formoving detection and Mobile IP information exchange that can be used inthe mobile communication system of FIG. 5.

FIG. 53 is diagram showing one exemplary configuration of an Internetaccess sub-system in the mobile communication system of FIG. 5.

FIG. 54 is diagram showing another exemplary configuration of anInternet access sub-system in the mobile communication system of FIG. 5.

FIG. 55 is a diagram showing an exemplary configuration of a routingheader to be used for the purpose of routing in the mobile communicationsystem of FIG. 5.

FIG. 56 is a diagram showing an exemplary mail transfer configuration inthe mobile communication system of FIG. 5.

FIG. 57 is a sequence chart showing an exemplary mail transfer operationprocedure in the mobile communication system of FIG. 5.

FIG. 58 is a diagram showing an exemplary WWW server accessconfiguration in the mobile communication system of FIG. 5.

FIG. 59 is a sequence chart showing an exemplary WWW server accessoperation procedure in the mobile communication system of FIG. 5.

FIG. 60 is a diagram showing an exemplary Internet connection operationin the mobile communication system of FIG. 5.

FIG. 61 is a sequence chant showing a data transmission procedure in thecase of setting up a connection to a media conversion server in themobile communication system of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, with references to the drawings, the preferred embodiment of arouter device, a datagram transfer method, and a communication systemaccording to the present invention will be described in detail.

FIG. 5 shows an exemplary basic configuration of a communication systemaccording to this embodiment. The communication system of FIG. 5 has aconfiguration in which a mobile communication network and an IP network(Internet) are connected to radio base stations, where a cellularterminal 227 is operated by the conventional mobile communicationmechanism for providing communication service. Details of communicationsby the cellular terminal 227 via the radio base stations and the mobilecommunication network will be described later. Here, the operation of amobile terminal 201 for carrying out communications via radio basestations and mobile supporting routers (abbreviated hereafter as MSR)according to the present invention will be described first.

The Internet access type communication system of FIG. 5 comprises: amobile terminal (MS) 201 which is at least capable of transmitting andreceiving IP packets; radio base stations (BTS) 202, 203, 210 and 211for transmitting and receiving data through radio channels with respectto the mobile terminal (MS) 201; mobile supporting routers (MSR) 220 and221 which are router devices supporting the handoff function (mobilityfunction) between the radio base stations where the MSR 220 accommodatesthe radio base stations 202 and 203 while the MSR 221 accommodates theradio base stations 210 and 211; a gateway (GW) 223 connected betweenInternet 224 and the MSRs 220 and 221; Internet 224 which functions as abackbone network and an IP terminal 225 connected to Internet 224.

The cellular terminal 227, the mobile terminal 201, the radio basestations 202, 203, 210 and 211 constitute a radio access sub-system inthe communication system of FIG. 5, in which radio communications arecarried out by efficiently allocating radio resources using the multipleaccess scheme such as TDMA (Time Division Multiple Access) scheme orCDMA (Code Division Multiple Access). In the radio section, functionalchannels are defined as shown in FIG. 6. These functional channels havethe well known functions as described in the RCR Standard STD-27, forexample.

The mobile terminal 201 is a terminal which is capable of carrying outpacket communications such as those of IP at least, by making randomaccesses or setting up radio channels with respect to the radio basestations 202, 203, 210, and 211.

The cellular terminal 227 is a terminal which is capable of carrying outchannel switching type communications such as those of speech at least,by setting up radio channels with respect to the radio base stations202, 203, 210 and 211 and utilizing the mobile communication network.

Each of the radio base stations 202, 203, 210 and 211 is capable ofbeing connected through radio channels with both the mobile terminal 201and the cellular terminal 227, and has a function (DMUX) fordemultiplexing and distributing data from the mobile terminal 201 to theMSRs and data from the cellular terminal 227 to the mobile communicationnetwork, and a function (MUX) for multiplexing data transmitted from theMSRs and the mobile communication network.

Note that the mobile terminal 201 and the cellular terminal 227 notifyrespective system configuration information and system parameterinformation to these radio base stations 202, 203, 210 and 211, so as toenable communications with the mobile communication network and the IProuting network, respectively.

FIG. 6 shows an exemplary case of using radio interfaces between themobile terminals and the radio base stations, but it is also possible toutilize various types of radio interfaces for the mobile communicationsystem as currently proposed.

On the other hand, the MSRs 220 and 221, the gateway 223 and Internet224 constitute a transmission sub-system in the communication system ofFIG. 5.

Each of the MSRs 220 and 221 is a router device which is capable ofswitching the transfer target at IP level at least when the mobileterminal 201 moves over the radio base stations connected to this MSR,and has a cut-through path set up/release function and a datalink layerlevel switching function for realizing a switching at VPI/VCI (VirtualPath Identifier/Virtual Channel Identifier) level, in addition to the IPlevel transfer target switching.

Moreover, each of the MSRs 220 and 221 also has an ATM switch functionfor providing the PVC (Permanent Virtual Connection) service capable ofbidirectional communications by executing the ATM cell exchangeprocessing by the ATM protocol according to the ITU-T recommendationI.361, as well as the SVC (Switched Virtual Connection) serviceaccording to the ATM Forum and ITU-T recommendation, and is capable ofrealizing any of one-to-one, one-to-N, and broadcast connection formsaccording to PVC/SVC.

The gateway 223 is a gateway device that at least has a function forconverting private IP addresses into global IP addresses (such as NAT:IP Network Address Translator, RFC 1631) and the Firewall function, inaddition to the functions of the MSR described above, as it is connectedto Internet 224 which is the global IP network.

Internet 224 is the global network that has been expanded to acommercial network connecting 173 countries around the world, 100million users, and 9.47 million host computers by January 1996, In whichthree network groups of the commercial Internet group such as IIJ, thePC communication network group such as NIFTY-Serve, and the academicInternet group such as WIDE are inter-connected and data are routedaccording to global IP addresses. In Internet 224, various applicationservices including information transfer type services such as E-mail andFile Transfer, information search type service such as Net News,information providing type service such as WWW, and instantaneousdialogue type service such as Telnet are already realized.

Note that, among the mobile terminal, the radio base stations and theMSRs described above, radio and wire logical channels as shown in FIG. 7and FIG. 8 are defined, by which the transfer of user data (such as IPpackets) can be carried out in any of the formats shown in FIG. 7 andFIG. 8 through prescribed logical channels or logical channels set upon-demand. In FIG. 7, the configuration 1 uses an SVC setting betweenthe mobile terminal 201 and the radio base station 202 and an SVCsetting between the radio base station 202 and the MSR 220, theconfiguration 2 uses an SVC setting between the mobile terminal 201 andthe radio base station 202 and a PVC setting between the radio basestation 202 and the MSR 220, the configuration 3 uses a PVC settingbetween the mobile terminal 201 and the radio base station 202 and anSVC setting between the radio base station 202 and the MSR 220, theconfiguration 4 uses a PVC setting between the mobile terminal 201 andthe MSR 220, and the configuration 5 uses an SVC setting between themobile terminal 201 and the MSR 220.

The control sub-system in the communication system of FIG. 5 has thefollowing server and client functions (1) to (8).

(1) Location Moving Management Function (MM):

The location moving management function has a part or a whole of thefollowing functions:

-   -   a function for managing and storing location information such as        location registration;    -   a function for controlling start, response, response detection,        execution, etc. of the paging;    -   a function for carrying out start judgement processing and        execution of the handoff; and    -   a function for carrying out system information notification,        etc.

This location moving management function is a function for realizing thehandoff at the datalink layer level, and includes an MM1 functionprovided at the IP network and the mobile terminal 201 in order torealize the channel switching (handoff control) during the communicationof the mobile terminal 201, and an MM2 function provided at the mobilecommunication network and the cellular terminal 227 in order to realizethe channel switching (handoff control) during the communication of thecellular terminal 227.

These MM1 function and MM2 function may be realized by the same protocolat different server locations, or by different protocols. Also, the MM1function may be equipped with the paging response detection function,the handoff start judgement processing and execution function, and thesystem information notification function alone. Alternatively, the MM1function may be utilizing the other mechanism such as Mobile IP as thefunction for managing and storing location information such as locationregistration, and equipped with all the other functions described above.

(2) Mobile IP Function (HA, FA):

In order to support Mobile IP, it is necessary to provide a HA (HomeAgent) having a function for managing a current location information ata visited site of the mobile terminal 201 and an FA (Foreign Agent)having a function for registering a location information at a visitedsite of the mobile terminal 201 into HA.

In addition to the above noted function, HA also has a function fortransmitting IP packets to be transferred to the mobile terminal 201which is moving to a subnet outside the home network at which HA islocated, that is, IP packets destined to the home address (originaladdress at the home network before moving) of the mobile terminal 201,by encapsulating these IP packets in packets destined to the currentlocation address of the mobile terminal 201.

Also, in addition to the above noted function, FA also has a functionfor decapsulating encapsulated IP packets transferred from HA to thevisited site network to take out original IP packets, and transfer theoriginal IP packets to the datalink.

The Mobile IP protocol is defined in RFC 2002 and includes a mode whichuses a router called FA for delivering packets for the mobile terminal201 to its visited site, and a mode in which the mobile terminal 201itself plays a role of FA. Either mode can be used in this embodiment.

(3) Dynamic Address Allocation Function (DHCP):

The dynamic address allocation function is a function for allocating andreleasing addresses such as IP addresses temporarily. As a protocol forrealizing dynamic allocation of IP addresses, DHCP of RFC 1541 may beused, or a protocol for carrying out totally different dynamic IPaddress allocation/release may be used.

(4) Address Conversion Function (NAT):

The address conversion function is a function for converting private IPaddresses into global IP addresses, and the function of NAT of RFC 1631may be utilized, for example.

(5) Call Control Function (CC):

The call control function includes a function for setting up,maintaining, changing and releasing connection/call of ATM, etc., and afunction for carrying out call admission control based on radioresources, allocation/reservation control for radio and networkresources (rewriting of a radio channel-VPI/VCI correspondencemanagement table), QOS control, etc.

(6) Radio Management Function (RT):

The radio management function includes functions of radio resource/radioconnection control (selection, reservation, release, etc.), radiochannel monitoring, and handover related processing associated withradio quality change.

(7) Switch Control Function (SWC):

The switch control function includes a function for connecting,maintaining, changing, disconnecting ATM connection (rewriting a VPI/VCItable), traffic control function such as CBR, rt/nrt VBR, ABR, UBR, anda scheduling function and a priority control function for buffermanagement such as WFQ (Weighted Fair Queueing).

(8) Cut-through Path Setting Function (FANP):

The cut-through path setting function is a function for making a layer 2switch on a lower level layer handling the transfer processing of therouter device. Prior to the cut-through, the layer 2 information such asMAC address is exchanged by a specific protocol between terminals orrouter devices. Then, the router device realizes the transfer by settingup a cut-through path for by-passing through the layer 2 switch withoutbringing the processing up to the network layer (layer 3). Here, theFANP function may be used as the cut-through path setting function.

Next, the radio control channel configuration and wire control channelconfiguration shown in FIG. 6 to FIG. 8 will be described.

As shown in FIG. 6, the radio control channels are largely divided intothe common control channels and the individual control channels.

The common control channels are control channels to be utilized commonlyby the radio terminals existing within the radio zones of the radio basestations 202, 203, 210 and 211, by which each radio terminal transferscontrol information to the radio base stations by random accesses.Downlink common control channels can be used as general broadcastchannels or selective broadcast channels. The individual controlchannels are control channels allocated to the radio terminals inpoint-to-point fashion, which are allocated on-demand by requests fromthe radio terminals or requests from the radio base stations, by whicheach radio terminal transfers control information prior to communicationstart, and during communication.

On the other hand, control channels as shown in FIG. 8 are defined forthe wire interfaces.

The meta-signaling VC is a control channel used in carrying out aprocedure (meta-signaling procedure) for setting up/releasing signalingVC other than those set up in advance. The general broadcast signalingVC is a signaling VC for transferring control information in broadcastfashion toward all nodes, which is a unidirectional control channel froma network to terminals. The selective broadcast signaling VC is aunidirectional control channel from a network to terminal group for eachservice profile (which identify a group of similar terminalsaccommodated in the same interface according to extension numbers,transmission powers, service types, etc.). When this selective broadcastsignaling VC is used, there is a merit in that it is unnecessary toprocess unrelated arriving signals at a terminal and it is possible toaccommodate terminals using different signal protocols in the sameinterface. The point-to-point signaling VC is a signaling VC to be setup for each terminal which is capable of bidirectional communications.

Also, the exchange of control information between various types ofcontrol function modules/functions to be described below is carried outeither by utilizing the above described radio control channels and wirecontrol channels directly or by using the following control channels Ato F, each of which is defined as a single logical control channel bymapping both.

Control channel A: a control channel set up in advance or allocatedon-demand, between the mobile terminal and radio base station.

Control channel B: a control channel set up in advance or allocatedon-demand, between the mobile terminal and the MSR.

Control channel C: a control channel set up in advance or allocatedon-demand, between the mobile terminal and the gateway.

Control channel D: a control channel set up in advance or allocatedon-demand, between the radio base station and the MSR.

Control channel E: a control channel set up in advance or allocatedon-demand, between the MSRs.

Control channel F: a control channel set up in advance or allocatedon-demand, between the MSR and the gateway.

In each of these control channels A to F, a part of a whole of thegeneral broadcast channel, the selective broadcast channel, and thepoint-to-point channel are set up. These types of channels may be set upnot only in the control channel but also in the communication channel bydefault.

The general broadcast channel as defined above is effective when it isdesired to control a plurality of terminals or nodes simultaneously, butin the case of usage similar to LAN (the case in which control messagesare frequently broadcast in the MAC layer or the IP layer) it is alsopossible to use the general broadcast channel as defined above bymapping it to the broadcast channel for broadcasting in the MAC layer orthe IP layer that is used in the LAN.

Also, the selective broadcast channel can be mapped to PCH and BCCH, andit can also be used by mapping when it is desired to broadcast withinsubnet which is an IP routing unit. Besides that, it is possible totransmit information in a form of appropriately limited range whilemaking communications with clients easy by defining these channels incorrespondence to the logical broadcast areas of various servers. Asdescribed above, by mapping the subnet area to the selective broadcastchannel, it becomes sufficient to transmit the agent advertisementmessage of FA to this selective broadcast channel, so that the very goodmatching can be realized. In other words, the agent advertisementmessage of FA is to be broadcast within the subnet, and when oneselective broadcast channel is set as a channel for broadcasting withinthe subnet in advance, the agent advertisement message can be broadcastwithin this subnet by simply transmitting the agent advertisementmessage to this selective broadcast channel.

Note that the above described general broadcast channel and selectivebroadcast channel are basically downlink (network→terminal)unidirectional channels, and uplink (terminal→network) unidirectionalchannel as defined in Ethernet is not defined In the conventionalcommunication system. However, in order to construct it within thecommunication system with good matching without changing the protocol ofthe computer system it is preferable to adopt a configuration in whichthe uplink general broadcast channel and selective broadcast channel aredefined and used by mapping with multicast and broadcast of the computernetwork.

Also, it is possible to broadcast the VPI/VCI value defined as theselective broadcast channel from BCCH of the radio base station, and usethat VPI/VCI value as a radio base station Identifier, a serveridentifier for identifying a service area of a server, a locationregistration area identifier, or a subnet identifier. For these controlchannels, channels already defined by the conventional signaling shouldbe used as much as possible, and when the conventionally unavailableuplink general broadcast channel and selective broadcast channel arenewly defined, they should be standardized, in order to achieve thegreater merit of connectability (which guarantees the proper operationin the case of connecting different systems or devices of differentvectors when identification number and significance (usage) of a channelto be used as the general broadcast channel or the selective broadcastchannel is specified by the standard specification and the like) andgenerality.

On the other hand, in the case of using a configuration in which theuser defined control channels are provided, the connectability andgenerality are inferior but there is a merit in that it has a greatflexibility as it is possible to freely define and utilize each channel.

Also, in order to realize the point-to-multipoint transfer and the likeeasily, Q.2931 provides messages called ADD PARTY and DROP PARTY so thatthe adding/dropping to/from multicast can be realized easily. By usingthem, it is also possible to realize a configuration in which channelscorresponding to the above described general broadcast VC and selectivebroadcast VC are formed and utilized for the similar usage and purpose.

Also, the exchange of control information between a server and a clientother than various functions to be described below (functions not shownin figures) can be carried out similarly by using logical channelsdefined in advance, or logical channels set up on-demand from logicalchannels defined in advance. In this control channel, a part or a wholeof the general broadcast channel, the selective broadcast channel, andthe point-to-point channel will be set up.

Here, the radio base station has a configuration having a function fortransferring the control channel in the radio section to the uplinkbroadcast or multicast VC in the wire section. More specifically, theradio base station shown in FIG. 8 has a function for transferring acontrol channel such as SCCH or USCCH defined on some specific radiochannel to the general broadcast VC or the selective broadcast VC in thewire section, so that a control message transmitted by the mobileterminal 201 to the radio base station by using the control channel suchas SCCH or USCCH of the above noted specific radio channel istransferred to the general broadcast VC or the selective broadcast VCdefined in the wire section, and multicasted to some specific area orbroadcasted within some specific area. Here, it is possible to determinein advance that SCCH should be mapped to the multicast and the USCCHshould be mapped to the broadcast. Alternatively, instead of determiningwhich one to map for each logical channel in this manner, it is alsopossible to provide an identification information for identifying as towhich one to map on the physical slot or physical frame.

The radio base station has a configuration equipped with a similartransfer function for the downlink direction of MSR→radio basestation→mobile terminal as well.

There is also a configuration in which the transfer of the selectivebroadcast VC in the radio section and the wire section and the transferof the general broadcast VC in the radio section and the wire sectionare carried out by setting up the general broadcast VC and the selectivebroadcast VC in VPI/VCI of the radio section similarly as in VPI/VCI ofthe wire section. In this case, a control message transmitted to theradio base station by using any radio channel and any logical channelwill be multicasted or broadcasted to some specific area as theselective broadcast VC or the general broadcast VC as long as It is insome specific VPI/VCI.

FIG. 9 shown an exemplary management architecture. The managementsub-system shown in FIG. 9 comprises an IP private network managementsystem and a mobile communication network management system, where theIP private network management system is managed by using NMP/UDP/IPwhich are the standard management protocols of Internet, while themobile communication network management system is managed by using CMIP(Common Management Information Protocol). This management sub-system canbe in forms of: an M1 interface which is an interface for managing ATMrouters, etc., each of which formed by installing an ATM interfaceadaptor card to an ATM terminal (server) or a general purpose router; anM2 interface which is an interface for managing the private ATM switch,the MSR, and the gateway; an M3 interface which is a managementinterface for the IP private network management system and the mobilecommunication network management system; and an M4 interface by whichthe the mobile communication network management system manages themobile communication network.

The private IP network management system is the M3 interface by whichthe mobile communication network can manage a part of the privatenetwork virtually. A typical MIB (Management Information Base) of theabove described M1/M2/M3 interface is defined by IETF as RFC 1695:“Definitions of Managed Objects for ATM Management Version 8.0 usingSMIv2”.

The above described management sub-system has a configuration in whichthe management of the radio access sub-system is added to a framework ofthe conventional wire network management, where the following managementitems (1) to (5) are added as the radio characteristic MIB in additionto the conventional M1 interface.

(1) Radio Traffic Management:

This periodically monitors a utilization state of each radio link, abandwidth allocation state, a number of passing packets, and a number ofpacket errors, while carrying out the monitoring of traffic in thespecified connection.

(2) Radio Communication Quality Management (Radio System PerformanceManagement):

This carries out the monitoring of communication quality (FER: FrameError Rate, BER: Bit Error Rate, SIR: Signal to Interference Ratio,etc.) of each radio link, as well as the monitoring of synchronizationestablishing state.

(3) Radio Trouble Management:

This carries out the monitoring of an occurrence state for troubles ineach radio link or node such as electrical state and transmission error.For example, it can detect such a case where a building or the like isbuilt after the base station is placed so that the regular shadowingoccurs and causes some trouble for communications. It can eliminate thetrouble by changing the radio system configuration such as switching theantenna direction remotely, using the radio system configurationmanagement to be described below.

(4) Radio System Configuration Management:

This carries out various types of setting and changing of systemparameters and the like for carrying our radio management/control suchas a number of radio channels, a sector selection state, an antennaswitching control, and a synthesizer switching control for each node(radio base station), and a display of each node state. In addition,this can also carry out setting of the transmission power control, etc.Moreover, this makes it possible to change the configuration of a radiobase station to which accesses are concentrated so that there is ashortage of radio channels compared with the other radio base stations,in the radio traffic management of (1) described above.

(5) Radio System Charge Management:

This monitors the connection set up time (especially the radio channeloccupation time in the radio section) or the IP address allocation timeand the IP datagram transfer amount in order to carry out the timecharging based on the monitored time and the amount charging based onthe monitored amount. In addition, this also carries out the secretmanagement, etc.

Here, the timing for carrying out the addressallocation/registration/release, and the connection set up/release canbe at a time of power ON, or at a time of standby and at a time locationregistration, or else at a time of call origination or call termination,and it is expected that whichever is cheapest at a time of carrying outdata transmission and reception will be adopted depending on thecharging schemes. For this reason, a concrete method for realizing theabove described feature and at what timing should the addressallocation/registration/release and the connection set up/release becarried out in that case will be described here in relation to servicesas well.

FIGS. 10A and 10B show a method of time charging based on the IP addressallocation time at a timing of the IP packet communication by the mobileterminal (W-MS) from the radio base station (W-BTS) via the MSR. In theradio communication system shown in FIGS. 10A and 10B, the time forwhich each mobile terminal maintains the IP address is calculated by theIP address allocation/release function (DHCP server function, forexample), and the charge related information is collected by exchangingcharge related information messages by SNMP between the maintenancecenter management terminal and the MSR. The collection of the chargerelated information can be realized by a method of polling from themaintenance center management terminal to each MSR or a method ofnotification from the MSR to the maintenance center management terminalby trap, and either method or their combination may be used.

FIGS. 10A and 10B use a configuration in which the role of the IPnetwork management system of FIG. 9 is also played by the maintenancecenter management terminal, where this management terminal has a CMIPfunction for carrying out the charge management within the mobilecommunication network in addition to SNMP.

Here, in the case where this maintenance center management terminal isconnected to an SSP/SCP, the charge information is exchanged through aroute shown in FIG. 10A or FIG. 10B. In such a case of the time chargingbased on the IP address allocation time, it is preferable to have the IPaddress allocated at a time of call origination or call termination,rather than at a time of power ON or at a time of standby and at a timeof location registration, and release the IP address at a time ofdisconnection.

On the other hand, FIG. 11 shows a method in which the radio basestation (W-BTS) calculates and manages the time and the number of radiochannels allocated to each mobile terminal, and the charge informationis exchanged between the maintenance terminal of the radio base stationand the maintenance center management terminal. In this case, the IPaddress allocation time is unrelated to the charge, so that the IPaddress may be allocated at a time of power ON, at a time of standby andat a time of location registration, or at a time of call origination orcall termination.

Now, the manner by which the IP address allocation/release functionprovided in the MSR as described above calculates the time for which theIP address is maintained will be described. The method for calculatingthe time for which the IP address is maintained can be, for example, amethod in which the time at which the IP address is allocated to themobile terminal and the time at which the IP address is released by themobile terminal are stored, and a message containing timestamps forthese allocation start and allocation end is notified to the MSR at atime of IP address release so that the MSR calculates the maintainedtime from the start time and the end time indicated in the receivedmessage.

The IP address allocation/release operation will be carried out asfollows. First, an IP address allocation request message containing aterminal ID is transmitted from the mobile terminal to the MSR. Uponreceiving this IP address allocation request message, the MSR determinesan IP address to be allocated to that mobile terminal, and registers itto an IP address allocation management table for managing acorrespondence between the terminal ID and the IP address, and thentransmits an IP address allocation response message containing at leasta set of the terminal ID and the IP address. Upon receiving this IPaddress allocation response message, the mobile terminal stores the IPaddress allocation start time.

Subsequently, the mobile terminal stores the end time at a time ofending communication, and an IP address release request messagecontaining the terminal ID, the IP address, the allocation start time,and the end time is transmitted from the mobile terminal to the MSR.Upon receiving this IP address release request message, the MSRcalculates the IP address allocation time from the start time and theend time and stores it, and transmits an IP address release responsemessage to the mobile terminal. Upon receiving this IP address releaseresponse message, the mobile terminal clears the corresponding IPaddress allocation start time and end time stored therein. If the IPaddress release response message is not received, the IP address releaserequest message is re-transmitted.

The method in which the mobile terminal transmits a message containingthe allocation start time and end time to the MSR and the MSR calculatesthe IP address allocation time from the received message has beendescribed above, but it is also possible to use a method in which themobile terminal calculates the IP address allocation time from theallocation start time and end time and transmits a message containingthe calculated IP address allocation time to the MSR.

These methods are directed to the case in which the mobile terminalstores the IP address allocation start time and end time or calculatesthe IP address allocation time and notifies the MSR, but the chargingcannot be made by these methods in the case where the mobile terminalhas moved out of zone. In order to resolve this problem, there is a needto make it possible to realize the charging based on the IP addressallocation time at the MSR even when there is no notification from themobile terminal as the mobile terminal has moved out of zone, inaddition to the method in which the mobile terminal stores the IPaddress allocation start time and end time or calculates the IP addressallocation time and notifies the MSR.

As a method for resolving this problem, it is possible to use a methodin which the the IP address allocation/release function of the MSRdefines a lease time for which the IP address is leased to the mobileterminal, and manages the IP address allocation using a lease timer suchthat the IP address allocation with respect to the mobile terminal isreleased when the extension/renewal of the lease time is not requestedfrom the mobile terminal within this lease time.

More specifically, this method can be realized as a method in which theDHCP server function is provided in the MSR and the MSR (DHCP server)calculates the elapsed time of the lease time according to the leasetime negotiated between the mobile terminal and the MSR (DHCP server) ata time of IP address allocation by the DHCP and its extension/renewal.In the following, the detailed operation in this case will be described.

The mobile terminal determines the lease time using the DHCP REQUESTmessage transmitted to the DHCP server function of the MSR and the DHCPACK/NAK, and requests the extension of the lease time by the DHCPREQUEST message when the communication cannot be finished within a rangeof the lease time. Upon receiving this DHCP REQUEST message forrequesting the extension, the MSR (DHCP server) clears the lease timerafter the elapsed time indicated by the lease timer is added to theimmediately previous total elapsed time. Also, upon receiving the DHCPRELEASE message, the MSR (DHCP server) calculates the IP addressallocation time by adding the elapsed time indicated by the lease timerto the immediately previous total elapsed time.

When the DHCP REQUEST message or the DHCP RELEASE message from themobile terminal is not received by the DHCP server before the timeout ofthe lease timer, the IP address allocation time is calculated by addingthe lease time to the immediately previous total elapsed time. Here, thecase where the IP address allocation/release function such as the DHCPserver function is provided in the MSR has been described, but it isalso possible to carry out the charging based on the IP addressallocation time by the similar method even in the case where the IPaddress allocation/release function such as the DHCP server function isprovided separately from the MSR.

In the above, the schematic configuration (configuration of the radioaccess sub-system and the transmission sub-system) of the physical part(hardware part) and the schematic configuration (configuration of themanagement sub-system and the control sub-system) of the logical part(software part) of the communication system according to this embodimentas shown in FIG. 5 have been described. Next, the handoff controloperation of the MSR will be described.

The handoff control operation comprises a moving detection (handofftrigger detection) phase F1, a visited site judgement/notification phaseF2, and an address/connection changing phase F3, which are executed inan order of F1→F2→F3, and the data transfer (IP packet transfer) to thevisited site connection is carried out after the execution of theaddress/connection changing phase F3 is completed. Here, the datatransfer to the originally located site connection may be continuedduring the handoff operation, or stopped in the case of datacommunication for which the real time nature is not required, or elseswitched between these two options according to the communicationquality request.

The moving detection phase F1 is a phase for detecting the movingbetween physical devices (moving between base stations, moving betweenMSRs) and the moving between functional modules (moving between subnets(FAs), the moving between DHCPs).

Here, the moving between base stations can be detected based on theradio link quality degradation between the base station and the mobileterminal, or the fact that the base station ID (BS ID) that isperiodically notified from the radio base station becomes different. Theformer case can be realized as a terminal initiative type in which thedetection is made by the terminal or a base station initiative type inwhich the detection is made by the base station, whereas the latter caseis going to be the terminal initiative type.

Also, the moving between the functional modules can be detected based onthe fact that various server IDs such as subnet ID (FA ID) and DHCPserver ID that are periodically notified from the radio base station orfrom the MSR via the radio base station become different. This detectionof the moving between functional modules is basically the terminalinitiative type, similarly as in the case of detecting the movingbetween base stations based on the fact that the base station ID becomesdifferent.

The visited site judgement/notification phase F2 is a phase fornotifying which identifier of which mobile terminal has changed how whenthe moving is detected, and judging the visited site of the mobileterminal. In the case of the terminal initiative type, the mobileterminal 201 is carrying out the detection of the moving and thejudgement of the visited site so that when the moving is detected themobile terminal carries out the operation to notify the own terminal IDand ID values at the visited site (as well as at the originally locatedsite if necessary) of various IDs (base station ID, MSR ID, subnet ID,DHCP server ID) that are changed, to the MSR or a server, Agent, orgateway that needs to switch its operation, in a form of a handoffrequest message. Alternatively, it is also possible to adopt aconfiguration in which the handoff request message is transmitted to theMSR, and the MSR that received this handoff request message notifiesthis to the servers corresponding to the IDs that are changed on behalfof the mobile terminal 201.

The base station initiative type can basically detect only the movingbetween base stations, so that the moving is detected by the radio basestation and the MSR judges the visited site. Namely, they operate as inthe following (1) to (4).

(1) The radio base station detects the moving of the mobile terminal 201according to the degradation of its radio link quality, and notifiesthis fact along with the terminal ID of the mobile terminal 201 and thebase station ID of this radio base station which made the detection, tothe MSR in a form of the handoff request message.

(2) Upon receiving this handoff request message, the MSR figures outneighboring radio base station area of the radio base station accordingto the value of the base station ID of the radio base station asdescribed within that handoff request message, and transmits a radiolink state measurement request message in a form containing the terminalID as described within that handoff request message to each radio basestation within the neighboring radio base station area.

(3) Upon receiving this radio link state measurement request message,each radio base station figures out the mobile terminal 201 according tothe terminal ID contained within that message, measures the radio linkquality between this base station and the mobile terminal 201, andnotifies the measurement result along with the terminal ID, to the MSRin a form of a radio link state measurement response message.

(4) Then, the MSR judges a radio base station that covers an area towhich the mobile terminal 201 has moved according to the radio linkstate measurement response messages transmitted from the radio basestations within the neighboring radio base station area.

The address/connection changing phase F3 is a phase for carrying out therewriting of the address management/conversion table (DHCP table, NATtable) and the connection management table (ARP table, VPI/VCI table)that are being set up, the address allocation and release, and theconnection set up and release, according to the change of various IDs(base station ID, MSR ID, subnet ID, address server ID).

In the address/connection changing phase F3, the address changing(allocation, release) and the connection changing (set up, release) arecarried out first (address changing phase, connection changing phase),and then the updating of the address management/conversion table and theconnection management table is carried out (management table updatingphase).

Here, either one or both of the connection changing and the addresschanging will be carried out, and in the case where both of them to beare carried out, either one may be changed before the other one or bothof them may be changed simultaneously if it is possible to change bothof them simultaneously.

Here, the re-call origination type handoff will be realized in the caseof carrying out the set up of the visited site connection after therelease of the originally located site connection, or the operation totemporarily becoming the multicast state and then returning to theunicast transfer state will be realized in the case of carrying out therelease of the originally located site connection after the set up ofthe visited site connection. The same is also true for the addresschanging as well.

Also, in the case of the moving over MSRs, besides the methods utilizingMobile IP or VIP, the handoff can be realized by a method in which thehandoff due to the moving of the terminal occurs by using the Link Statetype routing protocol such as PNNI routing protocol for example betweenthe MSRs and the change of transfer route is notified to thecorresponding MSR. In this case, it is necessary to update the routingtable in addition to the connection management table and the addressmanagement table.

In the above, the operation procedure for the handoff control by the MSRhas been described. Next, the concrete examples of a table configurationfor the MSR and a method for setting up a connection between the MSR andthe mobile terminal will be described.

First, with references to FIG. 12 to FIG. 14, the table updatingoperation at a time of the handoff control operation in the case ofusing the connection set up as in (configuration 4) of FIG. 7 (where aPVC is set up between the MSR and the mobile terminal) will bedescribed. FIG. 12 shows a concrete example of the handoff controloperation by the MSR. The radio communication system shown in FIG. 12comprises the Internet 224, the MSR 220, the radio base stations 202 and203, and the mobile terminal 201, where the MSR 220 has a connectionmanagement table (ARP table) for managing a correspondence between IPaddress and VPI/VCI, and each of the radio base station 202 and 203 hasa VPI/VCI-radio channel management table.

Also, in the radio communication system shown in FIG. 12, the controlchannel B as defined above and the communication channel are set up inadvance in the manner of (configuration 4) of FIG. 7, and it is assumedthat at least the base station ID, a PVC of the control channel B {a setof (radio CH, VPI/VCI)} and a PVC of the communication channel {a set of(radio CH, VPI/VCI)} are notified from each radio base station.

In FIG. 12, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVCs {PVC1 (radio CH=A, VPI/VCI=a), PVC2 (radioCH=B, VPI/VCI=b)} that are set up between the MSR 220 and the mobileterminal 201.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203, the procedure forswitching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described. Here, it is assumed that the MSR 220 isconstituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 notifies a handoff requestmessage containing IP address =Y of the mobile terminal 201 andVPI/VCI=b of PVC2 to the MSR 220, using the control channel B of theradio base station 203 which is the radio base station used after themoving. Upon receiving this handoff request message, the MSR 220 updatesthe connection management table (ARP table) shown in FIG. 12 accordingto IP address=Y and VPI/VCI=b contained within this handoff requestmessage.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2.In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion message as a trigger, the MSR 220 may transmit ahandoff completion message (which contains information contained in thehandoff request message such as IP address=Y and VPI/VCI=b) to themobile terminal 201, using the control channel B.

The example of FIG. 12 is directed to the case of using a configurationthat contains IP address and VPI/VCI for the handoff request message tobe transmitted from the mobile terminal 201 to the MSR 220, where IPaddress is used as an identifier (terminal ID) capable of identifyingthe terminal while VPI/VCI is used as an identifier (base station ID)indicating a location of a visited site of the terminal. In this case,the IP address can be either a global IP address or a private IPaddress, and also can be either a fixed IP address or a dynamicallyallocated IP address.

Note that when the fixed IP address is used as the terminal ID, itsuffices to carry out the updating of the ARP table exactly as in thehandoff control operation of FIG. 12, and even when the IP address isdynamically allocated by the MSR 220, it suffices to carry out theupdating of the ARP table similarly as in the case of using the fixed IPaddress because there is no IP address change for the moving within theMSR 220 which is constituting a single subnet as shown in FIG. 12.

However, when the MSR 220 constitutes plural subnets so that the IPaddress changes in conjunction with the moving, it is necessary tocancel a VCI corresponding to the old IP address and register a VCIcorresponding to the new IP address so that it is necessary to use thehandoff request message that at least contains the old IP address and(new IP address, VPI/VCI) set. In such a case where the terminal ID istemporarily allocated and has a possibility of being changed inconjunction with the moving, there is a need to notify the old terminalID as well when the change occurs, whereas in the case where theterminal ID is fixedly allocated or temporarily allocated but has nopossibility of being changed in conjunction with the moving, it sufficesto notify a value of the base station ID corresponding to the terminalID.

Here, the old IP address is also notified in order to cancel a VCIcorresponding to the old IP address, but when a timer as shown in FIG.12 is used, a VCI corresponding to the old IP address can be cancelledby the timeout of the timer, without requiring the notification of theold IP address. In this case, however, when the DHCP and the likeallocates the same IP address before its registration is cancelled onthe table, there arises a problem that the IP packet transmission willbe started erroneously toward VPI/VCI that has already been set incorrespondence.

In order to resolve this problem, the following three methods (1) to (3)are available.

(1) A method in which an IP address is returned to an idle IP addressmanagement queue from which the DHCP and the like carries out thedynamical IP address allocation only when the timeout of the IP-VPI/VCItable occurs and the registration is cancelled.

(2) A method in which the allocation is made from an IP address that isremaining in the idle IP address management queue for long time ratherthan immediately allocating an IP address for which the dynamical IPaddress allocation has been just released. (This can be realized byoperating the idle IP address management queue in First In First Outfashion rather than Last In First Out fashion.)

(3) A method in which a newly allocated IP address is always registeredin correspondence to the current location. By always carrying out theoperation to register a VPI/VCI value corresponding to the base stationID when an IP address is allocated, it becomes possible to avoid theerroneous delivery.

Note that the methods using a VPI/VCI value as the base station ID havebeen described here, but this base station ID is an information which isperiodically notified from the radio base stations 202 and 203. ThisVPI/VCI value to be used as the base station ID may not necessarily be asingle value and the radio base station may notify a plurality ofVPI/VCI values. In such a case, it suffices for the terminal to selectone of a plurality of VPI/VCI values randomly for example, and notifyit. In such a case of defining a plurality of VPI/VCI values as the basestation ID, by mapping each VPI/VCI value to a corresponding serviceclass and managing the number of users that can use each VPI/VCI value,there is a merit in that it becomes possible to accommodate many userswhile maintaining the communication quality of each service class.

As described, the case where the MSR 220 constitutes plural subnets sothat the IP address changes in conjunction with the moving requires theoperation different from the case where the MSR 220 constitutes a singlesubnet so that the IP address does not change in conjunction with themoving.

In addition, in such a case where the dynamical IP address of the mobileterminal 201 changes within the MSR 220, in order to make the IP addressof the mobile terminal 201 appears as if it is not changing from aviewpoint of Internet 224, it is necessary to provide an IP addressconversion function and an IP address conversion table for the purposeof converting an IP address (IP address=G) to be used in making anaccess to the mobile terminal 201 between Internet 224 and the MSR 220into an IP address to be used in making an access between the MSR 220and the mobile terminal 201.

In the following, the concrete example of the handoff control operationin the case where the MSR 220 constitutes plural subnets will bedescribed with reference to FIG. 47. The radio communication systemshown in FIG. 47 comprises the Internet 224, the MSR 220, the radio basestations 202 and 203, and the mobile terminal 201, where the MSR 220 hasa connection management table (ARP table) for managing a correspondencebetween IP address and VPI/VCI, and each of the radio base station 202and 203 has a VPI/VCI-radio channel management table.

Also, in the radio communication system shown in FIG. 47, the controlchannel B as defined above and the communication channel are set up inadvance in the manner of (configuration 4) of FIG. 7, and it is assumedthat at least the base station ID, a PVC of the control channel B {a setof (radio CH, VPI/VCI)}, a PVC of the communication channel {a set of(radio CH, VPI/VCI)}, and a subnet ID (or DHCP server ID) are notifiedfrom each radio base station.

In FIG. 47, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVCs {PVC1 (radio CH=A, VPI/VCI=a), PVC2 (radioCH=B, VPI/VCI=b)} that are set up between the MSR 220 and the mobileterminal 201.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 in FIG. 47, the procedurefor switching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described. Here, it is assumed that the MSR 220 isconstituting two subnets Aa and Ab.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged, and detects the need for re-allocation of IP address by thefact that the subnet ID (DHCP server ID) that is periodically notifiedfrom the radio base station has changed.

Then, the mobile terminal 201 notifies an IP address allocation requestcontaining at least the terminal ID=X of the mobile terminal 201 (andthe subnet ID=Ab if necessary) to the MSR 220, using the control channelB of the radio base station 203 which is the radio base station usedafter the moving.

Upon receiving this IP address allocation request message, the MSR 220allocates a new IP address, and updates the IP address corresponding tothe terminal ID=X from Y to Z in the IP address allocation table. Then,the MSR 220 transmits an IP address allocation response messagecontaining at least the terminal ID=X and a new IP address=Z to themobile terminal 201.

Then, upon receiving the IP address allocation response message, themobile terminal 201 transmits a handoff request message containing theold IP address=Y and the new IP address=Z of the mobile terminal 201 andVPI/VCI=b of PVC2 to the MSR 220, using the control channel B of theradio base station 203 which is the radio base station used after themoving. Upon receiving this handoff request message, the MSR 220 updatesthe connection management table (ARP table) shown in FIG. 47 bycancelling VPI/VCI=a corresponding to the old IP address=Y andregistering VPI/VCI=b corresponding to the new IP address=Z as containedwithin this handoff request message.

In addition, the MSR 220 updates the old IP address that is set incorrespondence to the IP address (IP address=G) to be used betweenInternet 224 and the MSR 220 in the IP address conversion table, to thenew IP address.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2.In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion message as a trigger, the MSR 220 may transmit ahandoff completion message (which contains information contained in thehandoff request message such as IP address=Y and VPI/VCI=b) to themobile terminal 201, using the control channel B.

It is also possible to use a configuration using NAT as the IP addressconversion function described above. Also, in the above, a configurationin which the IP address conversion function is provided in the MSR hasbeen described, but it is also possible to use a configuration in whichthe IP address conversion function is provided in the gateway of FIG. 5,for example, separately from the MSR. In this case, a message containingthe terminal ID=X, the old IP address, and the new IP address of themobile terminal is transmitted from the mobile terminal or the MSR tothe gateway, and the gateway is operated to update the old IP addressthat is set in correspondence to the IP address (IP address=G) to beused between Internet 224 and the gateway 223 in the IP addressconversion table, to the new IP address, according to this message. Theother operation is similar to that described above.

Here, the handoff request message containing the old IP address=Y, thenew IP address=Z, and VPI/VCI=b of PVC2 has been described above, butwhen a configuration in which the entry of the old IP address=Y is to bedeleted in the MSR 220 after the above described IP address reallocationoperation, the handoff request message used in FIG. 47 can have anidentical configuration to the handoff request message used in FIG. 12which contains the new IP address=Z and VPI/VCI=b of PVC2, andthereafter the operation similar to the handoff control operation ofFIG. 12 can be carried out.

In the above, the operation in the case where the MSR constitutes pluralsubnets and has a function for allocating/releasing IP addresses of theplural subnets (or plural DHCP server functions) has been described, andthe operation in the case where the mobile terminal moves over MSRs thatconstitute a single subnet can be regarded as exactly the sameoperation, by supposing that the radio base station 202 is connected tothe old MSR and the radio base station 203 is connected to the new MSRin the above description, except for the following operation.

Namely, it is necessary to transmit a message containing the old IPaddress=Y and the terminal ID=X from the new MSR to the old MSR, anddelete the entry of the old IP address=Y in the IP address allocationtable (X→NULL) as well as the entry of the old IP address=Y in the ARPtable at the old MSR which received that message.

Here, if each entry in the ARP table and the IP address allocation tableis managed by a timer, in the case of the moving over the MSRs asdescribed above, it is not absolutely necessary for the handoff requestmessage to contain the old IP address value and it is not necessary totransmit the above described message from the new MSR to the old MSR,and the deletion of an entry from each table can be done by timeout.

Also, in the example of FIG. 12, a configuration using IP address as theterminal ID and VPI/VCI as the base station ID has been described, butit is also possible to use a configuration which uses the terminal IDother than IP address, such as MAC address, mobility number (mobiletelephone number of E. 168 address and the like), and ATM address, forexample. In such a case, a correspondence management table for theterminal ID and IP address will be newly necessary in addition to theIP-VPI/VCI table of FIG. 12. Namely, it is necessary to figure out theIP address from the terminal ID, and updates the VPI/VCI valuecorresponding to that figures out IP address, so that two tables ofIP-terminal ID table and ARP table (IP-VCI correspondence managementtable) are necessary and the processing becomes two stages. In addition,in the case where the IP address is the temporarily allocated one, it isnecessary to receive a notification of the terminal ID, the new and oldIP addresses and the VCI as the base station ID, and cancel a VCI valuecorresponding to the old IP address and register a VCI valuecorresponding to the new IP address, while also updating the IP-terminalID correspondence management table, that is, updating the IP addressvalue corresponding to the terminal ID from the old IP address to thenew IP address.

In the case where the IP address is dynamically allocated one, there isa method which requires only a single stage processing rather than thecumbersome operation described above, which uses a unique terminal IDother than the IP address and a configuration having two tables of anIP-terminal ID table and a terminal ID-VCI table, as shown in FIG. 13.

In the case of this configuration, when the IP address is not changed ata time of handoff, it suffices to change only the VCI value in theterminal ID-VPI/VCI table. Moreover, the updating of the table is notcumbersome even in the case where the change of the IP address isnecessary, and the terminal ID-IP address correspondence managementtable and the terminal ID-VPI/VCI table can be updated simultaneously,so that there is a merit in that the updating operation can be a singlestage processing.

Here, the configuration in which the terminal ID-IP addresscorrespondence management table and the terminal ID-VPI/VCI table aredivided as two tables has been described, but it is possible to use atable configuration in which these two tables are combined into a singletable as shown in FIG. 13. Note however that, in the case where the MSRconstitutes plural subnets and there is a need to change the IP addressallocation even for the moving within one MSR, there arises a need todynamically allocate the IP address by the DHCP and the like withrespect to one terminal while carrying out the handoff operation withrespect to another terminal. In such a case, if there is only a singletable, the processing must be carried out in time division basis so thatthere is a demerit in that the processing time becomes long. In order toresolve this problem, it is necessary to provide the terminal ID-IPaddress correspondence management table separately from the terminalID-IP address-VPI/VCI table even though the other information is goingto be stored in overlap.

Next, the concrete example of the handoff control operation of the MSRwill be described with reference to FIG. 13.

The radio communication system shown in FIG. 13 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has an IP address allocation table formanaging a correspondence between IP address and terminal ID, and an ARPtable for managing a correspondence between terminal ID and VPI/VCI, andeach of the radio base station 202 and 203 has a VPI/VCI-radio channelmanagement table.

Also, in the radio communication system shown in FIG. 13, the controlchannel B as defined above and the communication channel are set up inadvance in the manner of (configuration 4) of FIG. 7, and it is assumedthat at least the base station ID, a PVC of the control channel B {a setof (radio CH, VPI/VCI)} and a PVC of the communication channel {a set of(radio CH, VPI/VCI)} are notified from each radio base station.

In FIG. 13, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVCs {PVC1 (radio CH=A, VPI/VCI=a), PVC2 (radioCH=B, VPI/VCI=b)} that are set up between the MSR 220 and the mobileterminal 201.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203, the procedure forswitching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described. Here, it is assumed that the MSR 220 isconstituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 notifies a handoff requestmessage containing the terminal ID=X of the mobile terminal 201 andVPI/VCI=b of PVC2 to the MSR 220, using the control channel B of theradio base station 203 which is the radio base station used after themoving.

Upon receiving this handoff request message, the MSR 220 updates the ARPtable shown in FIG. 13 according to the terminal ID=X and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2.

In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion message as a trigger, the MSR 220 may transmit ahandoff completion message (which contains information contained in thehandoff request message such as the terminal ID=X and VPI/VCI=b) to themobile terminal 201, using the control channel B.

Moreover, as shown in FIG. 14, there is also a case in which the basestation ID is used independently from VPI/VCI rather than using VPI/VCIas the base station ID. In this case, as the base station ID, an IFnumber which is a number for identifying a physical interface of the MSRmay be used, or a logical identifier to be set in one-to-one orone-to-multi correspondence with the IF number may be provided similarlyas the port number of the routing table. Here, in the case where thebase station ID independent from VPI/VCI is used, there is a merit inthat the same VPI/VCI can be reused among different base stations aslong as the uniqueness of the VPI/VCI value within the base station IDcan be maintained.

Also, in the case where the base station ID is allocated as a logicalidentifier, there is a need for a base station ID-IF numbercorrespondence table. This is necessary when the base station ID and theIF number are set in one-to-one correspondence but the IF number is notused as the base station ID or when the base station ID and the IFnumber are set in one-to-multi or multi-to-one correspondence. However,when the IF number is directly used as the base station ID, the basestation ID-IF number correspondence table is unnecessary.

Also, by using an identifier independent from the base station ID andthe IF number, there is a merit in that it becomes possible to realizevarious connection forms as shown in FIG. 15 (that is, the flexibilityregarding the connection form becomes high).

Note that even in the case of base station ID≠VCI as shown in FIG. 14,it is possible to use a table configuration having a timer (*α) or atable configuration of two divided tables (*β), just as in the case ofproviding the terminal ID separately from the IP address, and it ispossible to expect the similar effects as in the case of the basestation ID=VPI/VCI.

Next, the concrete example of the handoff control operation of the MSRwill be described with reference to FIG. 14.

The radio communication system shown in FIG. 14 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has an ARP table for managing acorrespondence among IP, base station ID and VPI/VCI, and each of theradio base station 202 and 203 has a VPI/VCI-radio channel managementtable.

Also, in the radio communication system shown in FIG. 14, the controlchannel B as defined above and the communication channel are set up inadvance in the manner of (configuration 4) of FIG. 7, and it is assumedthat at least the base station ID, a PVC of the control channel B {a setof (radio CH, VPI/VCI)} and a PVC of the communication channel {a set of(radio CH, VPI/VCI)} are notified from each radio base station.

In FIG. 14, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVCs {PVC1 (radio CH=A, VPI/VCI=a), PVC2 (radioCH=B, VPI/VCI=b)} that are set up between the MSR 220 and the mobileterminal 201.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 in FIG. 14, the procedurefor switching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described. Here, it is assumed that the MSR 220 isconstituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 notifies a handoff requestmessage containing the IP address=Y of the mobile terminal 201, the basestation ID=BS2, and VPI/VCI=a of PVC2 to the MSR 220, using the controlchannel B of the radio base station 203 which is the radio base stationused after the moving.

Upon receiving this handoff request message, the MSR 220 updates the ARPtable shown in FIG. 14 according to the IP address=Y, the base stationID=BS2 and VPI/VCI=a contained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2.

In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion message as a trigger, the MSR 220 may transmit ahandoff completion message (which contains information contained in thehandoff request message such as the IP address=Y. the base stationID=BS2 and VPI/VCI=a) to the mobile terminal 201, using the controlchannel B.

Moreover, it is also possible to use a configuration using a mappingmethod as shown in FIG. 16 for the terminal ID and the base station ID.Namely, a configuration using the VPI/VCI value as the terminal ID hasnot been described above, but the case of using the IP address (fixed,dynamical) which is a logical number and to be used in the routing hasbeen described so that the similar configuration may be used. Also, aconfiguration using the IP address or the connection set up address asthe base station ID have not been described above, but it is possible touse the operation similar to that in the configuration using VPI/VCI asthe base station ID in such cases.

The configuration using VPI/VCI and the like as the base station ID andthe terminal ID as shown in FIG. 16 has a drawback in that there is onlya lower flexibility when the cases of connection between the MSR and theradio base stations as shown in FIG. 15 are taken into account. comparedwith the case of the configuration using the base station ID and theterminal ID independently. However, it is possible to realize thestandby operation, the location registration operation, the handoffcontrol operation, the call origination connection operation, and thecall termination connection operation without any problem, when theconnection is limited.

In the above, the operation at a time of the handoff control in the caseusing the connection set up as in (configuration 4) of FIG. 7 has beendescribed with references to FIG. 12 to FIG. 14. Next, the handoffcontrol operation in the case using the connection set up as in any of(configuration 1) to (configuration 3) and (configuration 5) of FIG. 7in the system of FIG. 12 will be described.

First, the table changing operation at a time of the handoff controloperation in the case of using the connection set up as in(configuration 1) (SVC for radio section, SVC for wire section) of FIG.7 in the system of FIG. 12 will be described.

The radio communication system shown in FIG. 12 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has a connection management table (ARPtable) for managing a correspondence between IP address and VPI/VCI, andeach of the radio base station 202 and 203 has a VPI/VCI-radio channelmanagement table.

The difference between (configuration 1) and (configuration 4) is that,in (configuration 1), the VPI/VCI-radio channel management tableprovided in the radio base station 202 and 203 is in a configurationhaving a function for converting VPI/VCI in the wire section intoVPI/VCI and radio CH in the radio section or vice versa, and thatinformation periodically notified by the radio base station 202 and 203is in a configuration containing at least the base station ID and a PVCof the control channel A and/or the control channel B {a set of (radioCH, VPI/VCI)}.

In FIG. 12, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using SVC1A (radio CH=A, VPI/VCI=a) between themobile terminal 201 and the radio base station 202, SVC1a (VPI/VCI=a)between the radio base station 202 and the MSR 220, SVC2B (radio CH=B,VPI/VCI=b) between the mobile terminal 201 and the radio base station203, and SVC2b (VPI/VCI=b) between the radio base station 203 and theMSR 220, which are set up on-demand.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 in FIG. 12, the procedurefor switching from a state in which the IP packet communication withInternet 224 is carried out by using SVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingSVC2 will be described. Here, it is assumed that the MSR 220 isconstituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 sets up SVC2B (radio CH=B,VPI/VCI=b) in the radio section by transmitting a SETUP message to theradio base station 203 which is the radio base station used after themoving, and transmits a handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) tothe radio base station 203.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2b (VPI/VCI=b) in the wiresection by transmitting a SETUP message to the MSR 220, and updates theVPI/VCI-radio channel management table provided in the radio basestation 203 so as to set the wire section VPI/VCI=b, the radio sectionVPI/VCI=b, and the radio CH=B in correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section SVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1 to a communication using SVC2.

The case described above is directed to the method in which the mobileterminal 201 sets up the radio section SVC by transmitting the SETUPmessage to the radio base station 203 while transmitting the handoffrequest message to the radio base station 203, and using this as atrigger, the radio base station 203 transmits the handoff requestmessage to the MSR 220, but there is also a method in which the radiobase station 203 sets up the radio section SVC2B and the wire sectionSVC2b upon receiving the handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) fromthe mobile terminal 201. The operation in this case will be describednext.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2b (VPI/VCI=b) in the wiresection by transmitting a SETUP message to the MSR 220, while alsosetting up SVC2B (radio CH=B, VPI/VCI=b) in the radio section bytransmitting a SETUP message to the mobile terminal 201.

In addition, when the connection set up in the wire section and theradio section is completed, the radio base station 203 updates theVPI/VCI-radio channel management table provided in the radio basestation 203 so as to set the wire section VPI/VCI=b, the radio sectionVPI/VCI=b, and the radio CH=B in correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section SVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1 to a communication using SVC2.

It is also possible to use the method in which the wire section SVC setup is made by the MSR 220 rather than the radio base station 203. Theoperation in this case will be described next.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 sets up SVC2B (radio CH=B,VPI/VCI=b) in the radio section by transmitting a SETUP message to theradio base station 203 which is the radio base station used after themoving, and transmits a handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) tothe radio base station 203.

Upon receiving this handoff request message, the radio base station 203transmits it to the MSR 220. Upon receiving this handoff request messagefrom the radio base station 203, the MSR 220 takes this as a trigger andsets up SVC2b (VPI/VCI=b) in the wire section by transmitting a SETUPmessage to the radio base station 203, and updates the connectionmanagement table (ARP table) shown in FIG. 12 according to the IPaddress=Y contained within this handoff request message and VPI/VCI=bobtained by the connection set up described above.

In addition, when SVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1 to a communication using SVC2.

Also, the radio communication system shown in FIG. 12 may carry out thehandoff control operation as follows.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2B (radio CH=B, VPI/VCI=b) in theradio section by transmitting a SETUP message to the mobile terminal201, while also transmitting the handoff request message as receivedfrom the mobile terminal 201 to the MSR 220.

Upon receiving this handoff request message from the radio base station203, the MSR 220 takes this as a trigger and sets up SVC2b (VPI/VCI=b)in the wire section by transmitting a SETUP message to the radio basestation 203, and updates the connection management table (ARP table)shown in FIG. 12 according to the IP address=Y contained within thishandoff request message and VPI/VCI=b obtained by the connection set updescribed above.

In addition, when SVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1 to a communication using SVC2.

Next, the table changing operation at a time of the handoff controloperation in the case of using the connection set up as in(configuration 2) (SVC for radio section, PVC for wire section) of FIG.7 in the system of FIG. 12 will be described.

The radio communication system shown in FIG. 12 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has a connection management table (ARPtable) for managing a correspondence between IP address and VPI/VCI, andeach of the radio base station 202 and 203 has a VPI/VCI-radio channelmanagement table.

The difference between (configuration 2) and (configuration 4) is that,in (configuration 2), the VPI/VCI-radio channel management tableprovided in the radio base station 202 and 203 is in a configurationhaving a function for converting VPI/VCI in the wire section intoVPI/VCI and radio CH in the radio section or vice versa, and thatinformation periodically notified by the radio base station 202 and 203is in a configuration containing at least the base station ID and a PVCof the control channel A and/or the control channel B {a set of (radioCH, VPI/VCI)}.

In FIG. 12, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using SVC1A (radio CH=A, VPI/VCI=a) between themobile terminal 201 and the radio base station 202 which is set upon-demand, PVC1a (VPI/VCI=a) between the radio base station 202 and theMSR 220 which is set up in advance, SVC2B (radio CH=B, VPI/VCI=b)between the mobile terminal 201 and the radio base station 203 which isset up on-demand, and PVC2b (VPI/VCI=b) between the radio base station203 and the MSR 220 which is set up in advance.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 in FIG. 12, the procedurefor switching from a state in which the IP packet communication withInternet 224 is carried out by using SVC1A and PVC1a to a state in whichthe IP packet communication with Internet 224 is to be carried out byusing SVC2B and PVC2b will be described. Here, it is assumed that theMSR 220 is constituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 sets up SVC2B (radio CH=B,VPI/VCI=b) in the radio section by transmitting a SETUP message to theradio base station 203 which is the radio base station used after themoving, and transmits a handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) tothe radio base station 203.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and selects PVC2b (VPI/VCI=b) that is alreadyset up in the wire section, and updates the VPI/VCI-radio channelmanagement table provided in the radio base station 203 so as to set thewire section VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=Bin correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section PVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1A and PVC1a to a communicationusing SVC2B and PVC2b.

The case described above is directed to the method in which the mobileterminal 201 sets up the radio section SVC by transmitting the SETUPmessage to the radio base station 203 while transmitting the handoffrequest message to the radio base station 203, and using this as atrigger, the radio base station 203 transmits the handoff requestmessage to the MSR 220, but there is also a method in which the radiobase station 203 sets up the radio section SVC2B and the wire sectionPVC2b upon receiving the handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) fromthe mobile terminal 201. The operation in this case will be describednext.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and selects PVC2b (VPI/VCI=b) that is alreadyset up in the wire section between the radio base station 203 and theMSR 220, while also setting up SVC2B (radio CH=B, VPI/VCI=b) in theradio section by transmitting a SETUP message to the mobile terminal201.

In addition, when the connection set up in the wire section and theradio section is completed, the radio base station 203 updates theVPI/VCI-radio channel management table provided in the radio basestation 203 so as to set the wire section VPI/VCI=b, the radio sectionVPI/VCI=b, and the radio CH=B in correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section PVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1A and PVC1a to a communicationusing SVC2B and PVC2b.

It is also possible to use the method in which the wire section PVC setup is made by the MSR 220 rather than the radio base station 203. Theoperation in this case will be described next.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 sets up SVC2B (radio CH=B,VPI/VCI=b) in the radio section by transmitting a SETUP message to theradio base station 203 which is the radio base station used after themoving, and transmits a handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) tothe radio base station 203.

Upon receiving this handoff request message, the radio base station 203transmits it to the MSR 220. Upon receiving this handoff request messagefrom the radio base station 203, the MSR 220 takes this as a trigger andselects PVC2b (VPI/VCI=b) that is already set up in the wire sectionbetween the radio base station 203 and the MSR 220, and updates theconnection management table (ARP table) shown in FIG. 12 according tothe IP address=Y contained within this handoff request message andVPI/VCI=b obtained by the PVC selection described above.

In addition, when PVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1A and PVC1a to a communicationusing SVC2B and PVC2b.

Also, the radio communication system shown in FIG. 12 may carry out thehandoff control operation as follows.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2B (radio CH=B, VPI/VCI=b) in theradio section by transmitting a SETUP message to the mobile terminal201, while also transmitting the handoff request message as receivedfrom the mobile terminal 201 to the MSR 220.

Upon receiving this handoff request message from the radio base station203, the MSR 220 takes this as a trigger and selects PVC2b (VPI/VCI=b)that is already set up in the wire section between the radio basestation 203 and the MSR 220, and updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y containedwithin this handoff request message and VPI/VCI=b obtained by the PVCselection described above.

In addition, when PVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using SVC1A and PVC1a to a communicationusing SVC2B and PVC2b.

Next, the table changing operation at a time of the handoff controloperation in the case of using the connection set up as in(configuration 3) (PVC for radio section, SVC for wire section) of FIG.7 in the system of FIG. 12 will be described.

The radio communication system shown in FIG. 12 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has a connection management table (ARPtable) for managing a correspondence between IP address and VPI/VCI, andeach of the radio base station 202 and 203 has a VPI/VCI-radio channelmanagement table.

The difference between (configuration 3) and (configuration 4) is that,in (configuration 3), the VPI/VCI-radio channel management tableprovided in the radio base station 202 and 203 is in a configurationhaving a function for converting VPI/VCI in the wire section intoVPI/VCI and radio CH in the radio section or vice versa, and thatinformation periodically notified by the radio base station 202 and 203is in a configuration containing at least the base station ID and a PVCof the control channel A and/or the control channel B {a set of (radioCH, VPI/VCI)}.

In FIG. 12, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVC1A (radio CH=A, VPI/VCI=a) between themobile terminal 201 and the radio base station 202 which is set up inadvance, SVC1a (VPI/VCI=a) between the radio base station 202 and theMSR 220 which is set up on-demand, PVC2B (radio CH=B, VPI/VCI=b) betweenthe mobile terminal 201 and the radio base station 203 which is set upin advance, and SVC2b (VPI/VCI=b) between the radio base station 203 andthe MSR 220 which is set up on-demand.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 in FIG. 12, the procedurefor switching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1A and SVC1a to a state in whichthe IP packet communication with Internet 224 is to be carried out byusing PVC2B and SVC2b will be described. Here, it is assumed that theMSR 220 is constituting a single subnet AA.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 selects PVC2B (radio CH=B,VPI/VCI=b) that is already set up in the radio section between themobile terminal 201 and the radio base station 203 which is the radiobase station used after the moving, and transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2b (VPI/VCI=b) in the wiresection by transmitting a SETUP message to the MSR 220, and updates theVPI/VCI-radio channel management table provided in the radio basestation 203 so as to set the wire section VPI/VCI=b, the radio sectionVPI/VCI=b, and the radio CH=B in correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section SVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1A and SVC1a to a communicationusing PVC2B and SVC2b.

The case described above is directed to the method in which the mobileterminal 201 selects the radio section PVC while transmitting thehandoff request message to the radio base station 203, and using this asa trigger, the radio base station 203 transmits the handoff requestmessage to the MSR 220, but there is also a method in which the radiobase station 203 sets up the radio section PVC2B and the wire sectionSVC2b upon receiving the handoff request message (containing thecommunication protocol ID, the terminal ID=X, and the IP address=Y) fromthe mobile terminal 201. The operation in this case will be describednext.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and sets up SVC2b (VPI/VCI=b) in the wiresection by transmitting a SETUP message to the MSR 220, while alsoselecting PVC2B (radio CH=B, VPI/VCI=b) that is already set up in theradio section between the radio base station 203 and the mobile terminal201.

In addition, when the connection set up in the wire section and theradio section is completed, the radio base station 203 updates theVPI/VCI-radio channel management table provided in the radio basestation 203 so as to set the wire section VPI/VCI=b, the radio sectionVPI/VCI=b, and the radio CH=B in correspondence.

In addition, the radio base station 203 transmits the handoff requestmessage received from the mobile terminal 201 to the MSR 220 by addingthe wire section SVC2b (VPI/VCI=b) thereto. Upon receiving this handoffrequest message, the MSR 220 updates the connection management table(ARP table) shown in FIG. 12 according to the IP address=Y and VPI/VCI=bcontained within this handoff request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1A and SVC1a to a communicationusing PVC2B and SVC2b.

It is also possible to use the method in which the wire section SVC setup is made by the MSR 220 rather than the radio base station 203. Theoperation in this case will be described next.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 selects PVC2B (radio CH=B,VPI/VCI=b) that is already set up in the radio section between themobile terminal 201 and the radio base station 203 which is the radiobase station used after the moving, and transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y, as well as the radio CH=B, the radio sectionVPI/VCI=b if necessary) to the radio base station 203.

Upon receiving this handoff request message, the radio base station 203transmits it to the MSR 220. Upon receiving this handoff request messagefrom the radio base station 203, the MSR 220 takes this as a trigger andsets up SVC2b (VPI/VCI=b) in the wire section by transmitting a SETUPmessage to the radio base station 203, and updates the connectionmanagement table (ARP table) shown in FIG. 12 according to the IPaddress=Y contained within this handoff request message and VPI/VCI=bobtained by the connection set up described above.

In addition, when SVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1A and SVC1a to a communicationusing PVC2B and SVC2b.

Also, the radio communication system shown in FIG. 12 may carry out thehandoff control operation as follows.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 transmits a handoff requestmessage (containing the communication protocol ID, the terminal ID=X,and the IP address=Y) to the radio base station 203 which is the radiobase station used after the moving.

Upon receiving this handoff request message, the radio base station 203takes this as a trigger and selects PVC2B (radio CH=B, VPI/VCI=b) thatis already set up in the radio section between the radio base station203 and the mobile terminal 201, while also transmitting the handoffrequest message as received from the mobile terminal 201 to the MSR 220.

Upon receiving this handoff request message from the radio base station203, the MSR 220 takes this as a trigger and sets up SVC2b (VPI/VCI=b)in the wire section by transmitting a SETUP message to the radio basestation 203, and updates the connection management table (ARP table)shown in FIG. 12 according to the IP address=Y contained within thishandoff request message and VPI/VCI=b obtained by the connection set updescribed above.

In addition, when SVC2b (VPI/VCI=b) is set up in the wire section, theradio base station 203 updates the VPI/VCI-radio channel managementtable provided in the radio base station 203 so as to set the wiresection VPI/VCI=b, the radio section VPI/VCI=b, and the radio CH=B incorrespondence.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1A and SVC1a to a communicationusing PVC2B and SVC2b.

Finally, the table changing operation at a time of the handoff controloperation in the case of using the connection set up as in(configuration 5) (SVC for radio section and wire section withouttermination) of FIG. 7 in the system of FIG. 12 will be described.

In this case, the operation is similar to the the handoff controloperation in the case of (configuration 4) except that, instead ofcarrying out the operation by PVC selection, SVC2 is set up between themobile terminal 201 and the MSR 220 by transmitting a SETUP message fromthe mobile terminal 201 or the MSR 220.

For this reason, the difference between (configuration 5) and(configuration 4) is that, in (configuration 5), informationperiodically notified by the radio base station 202 and 203 is in aconfiguration containing at least the base station ID and a PVC of thecontrol channel A and/or the control channel B {a set of (radio CH,VPI/VCI)}, and that the connection set up address (such as ATM address,for example) of the MSR 220 is also notified in the case of setting up aconnection from the mobile terminal 201 with respect to the MSR 220, orthat the handoff request message also contains the terminal ID or theconnection set up address (such as ATM address, for example) of themobile terminal 201 in the case of transmitting a SETUP message from theMSR 220 to the mobile terminal 201.

Here, the allocation release of the radio channel and VPI/VCI withrespect to the originally located radio base station may be realizedaccording to a timer, or by notifying values of the radio channel andVPI/VCI to be released by the similar procedure as in the case ofallocating the radio channel and VPI/VCI, except for the difference inmessage types to be used.

Next, a method by which the base station detects the moving of themobile terminal and the MSR judges the visited site base station andcarries out the switching will be described.

In the base station initiative type handoff operation, the radio stationdetects the degradation of the radio communication quality such as thereceived signal strength of the mobile terminal, and notifies it to theMSR. Upon receiving this notification, the MSR asks the radio basestations in a surrounding zone to measure the radio state, and judgesthe visited site according to the measured radio state of collected fromeach radio base station. After the visited site is judged, the operationsimilar to the terminal initiative type handoff operation as describedabove is carried out.

Now, the concrete example of the handoff control operation by the MSRwill be described with reference to FIG. 50.

The radio communication system shown in FIG. 50 comprises the Internet224, the MSR 220, the radio base stations 202 and 203, and the mobileterminal 201, where the MSR 220 has a routing table for managing acorrespondence among destination IP, next IP and IF number, and an ARPtable for managing a correspondence between IP address and VPI/VCI, andeach of the radio base station 202 and 203 has a VPI/VCI-radio channelmanagement table.

Also, in the radio communication system of FIG. 50, at least a defaultVC (PVC) which is a VC to be utilized as a shared channel that is set upin advance is defined between the MSR and the radio base station, and atleast a pre-assigned radio channel (PVC) which is a radio channel thatis set up in advance is defined between the radio base station and themobile terminal. In addition, the control channel B as defined above andthe communication channel are set up in advance in the manner of(configuration 4) of FIG. 7, and it is assumed that at least the basestation ID (IF number), a PVC of the control channel B {a set of (radioCH, VPI/VCI)} and a PVC of the communication channel {a set of (radioCH, VPI/VCI)} are notified from each radio base station.

In FIG. 50, in the case where the mobile terminal 201 carries out the IPpacket communications with Internet 224, the IP packet communicationsare carried out by using PVCs {PVC1 (radio CH=A, VPI/VCI=a), PVC2 (radioCH=B, VPI/VCI=b)} that are set up between the MSR 220 and the mobileterminal 201.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203, the procedure forswitching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described.

First, the mobile terminal 201 detects the moving from the radio basestation 202 to the radio base station 203 by the fact that the basestation ID that is periodically notified from the radio base station haschanged. Then, the mobile terminal 201 notifies a handoff requestmessage containing the IP address=Y of the mobile terminal 201 (and thebase station ID=#2 if necessary) to the MSR 220, using the controlchannel B of the radio base station 203 which is the radio base stationused after the moving.

Upon receiving this handoff request message, the MSR 220 refers to therouting table according to the IP address=Y contained within thishandoff request message, and delete the entry of that IP address in theARP table #1 for the old base station ID=#1 while updating the entry ofthe IP address=Y in the routing table according to the IF number=#2 forwhich the handoff request is received. In addition, the MSR 220 figuresout (or selects) the default VC=b corresponding to the new base stationID=#2, and registers the IP address=Y and the VPI/VCI=b in the ARP table#2.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2.

In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion message as a trigger, the MSR 220 may transmit ahandoff completion message (which contains information contained in thehandoff request message such as the IP address=Y, the base stationID=#2, and VPI/VCI=b) to the mobile terminal 201, using the controlchannel B.

In the case where the value of PVC set up between the MSR 220 and themobile terminal 201 is notified by transmitting the handoff completionmessage from the MSR 220 to the mobile terminal 201 in this manner, itbecomes possible for the mobile terminal 201 to ascertain which PVCshould be used even when a plurality of communication PVCs are set upbetween the MSR 220 and the mobile terminal 201.

Also, it is possible to use some specific default VC for transfer if nodefault VC is registered in the ARP table. In such a case, there is noneed for the registration of the entry in the ARP table.

Next, the operation procedure of the mobile terminal 201 will bedescribed with references to FIG. 17 and FIG. 18. Here, the followingdescription is directed to an exemplary case in which the mobileterminal 201 turns the power ON outside of zone and then moves into anarea of the radio base station 202, and makes a call originationconnection to the IP terminal 225 after carrying out the locationregistration and IP address allocation operations, and then subsequentlymoves from the radio base station 202 to the radio base station 203 inthe communicating state and is disconnected at the radio base station203, and then subsequently there is a call termination from the IPterminal 225.

First, the operation of the mobile terminal 201 at a time of turning thepower ON outside of zone will be described with references to FIG. 19and FIG. 20.

FIG. 19 shows a state transition diagram for the operation of the mobileterminal 201. As shown in FIG. 19, the operation state of this mobileterminal 201 includes a standby operation state, a location registrationoperation state, a call origination operation state, a call terminationoperation state, a call end and disconnection operation state, and achannel switching during communication operation (handoff operation)state. In further detail, the terminal operation at a time of the powerON/standby is carried out according to the flow chart of FIG. 20 asfollows.

When the mobile terminal 201 turns the power ON outside of zone, itrepeats the operation to indicate that it is out of zone by carrying outthe operations (1) and (2) of FIG. 20. Here, The perch channel(dedicated control channel) used in (2) is a common control channel fortransmitting control information necessary for call set up, which is oneof the pre-assigned radio channel in FIG. 17 and FIG. 18.

Next, the operation of the mobile terminal 201 in the case of carryingout the location registration and IP address allocation by moving insideof zone from outside of zone will be described with reference to FIG.20. When the mobile terminal 201 moves inside of zone from outside ofzone, the operations (1) to (5) of FIG. 20 are carried out. Then, thelocation registration and IP address allocation operations are carriedout and a transition to the standby operation state is made.

Here, there is a method in which the location registration and IPaddress allocation operations are to be carried out at a time of callorigination or call termination connection, and there is also a methodin which the IP address allocation is carried out before switching tothe call termination control channel after receiving the broadcastchannel, and which timing is optimum for carrying them out depends onthe charging scheme described above and a relationship with the service.

For this reason, it is possible to use a configuration in which thelocation registration and IP address allocation operations can beexecuted at optimum execution timings in correspondence to the chargingscheme and a relationship with the service.

In addition, it is also possible to use a configuration in which timingsfor carrying out the location registration and IP address allocationoperations can be dynamically switched to the optimum timings dependingon the charging scheme and a relationship with the service.

Next, the location registration operation of the mobile terminal 201will be described.

The location/address registration operation includes a location/addressregistration detection phase and a location/address registrationexecution phase, and it is also possible to provide aresponse/confirmation phase after the location address registration. Thelocation/address registration execution phase may contain theregistration of address information for the purpose of setting up aconnection in addition to the registration of location information.

Using this location/address registration operation, it becomes possiblefor the MSR to carry out the VPI/VCI selection for PVC according to thelocation registration information, or the location confirmationoperation based on paging, and by registering the connection set upaddress such as ATM address, it becomes possible to realize the calltermination by entering into the connection set up operation at a timeof receiving an IP packet without requiring the location confirmationoperation.

Here, messages are exchanged between the mobile terminal 201 and the MSRfor the purpose of making the location registration, using thepre-assigned radio channel and the default VC channel (PVC) of FIG. 17and FIG. 18.

In the following, detailed concrete examples for the standby operation,the location registration operation, and the IP address allocationoperation will be described.

The standby operation state is an idle state during the operations forcall origination, call termination, location registration, etc., whilethe power of the mobile terminal 201 is turned ON, in which the mobileterminal 201 measures a received signal strength of each perch channel(dedicated control channel)(BCCH) stored within a memory by sequentiallyswitching the perch channels (dedicated control channels), and switchesto BCCH of the maximum received signal strength while receiving andstoring into the memory the information related to the channelstructure, the system information, etc.

Now the terminal operations (1) to (9) at a time of the power ON/standbywill be described with reference to FIG. 20.

(1) When the power of the terminal is turned ON, a radio communicationmodule (radio card, etc.) connected to the terminal body sequentiallyswitches perch channels (dedicated control channels) stored in a memoryand measures the received signal strength of each perch channel(dedicated control channel).

(2) When the received signal strength of every perch channel (dedicatedcontrol channel) is below a threshold, it is judges that the terminal islocated out of zone and an out of zone indication is made.

(3) When there is a perch channel (dedicated control channel) with thereceived signal strength above the threshold, the terminal is switchedto a perch channel (dedicated control channel) with the maximum receivedsignal strength.

(4) The broadcast channel (BCCH) transmitted through that perch channel(dedicated control channel) is received, and stored in a memory. At thispoint, the information broadcast from the radio base station includesthe radio base station ID, the MSR ID, the location registration areanumber, the random access (call origination control) channel number, thecall termination control channel number, the perch channel (dedicatedcontrol channel) number of neighboring base station, the regulationinformation (transmission probability, etc.), the system relatedinformation such as control channel structure information (broadcastinformation related to the mobile communication system and broadcastinformation related to the packet communication), etc. Besides that, itis also possible to broadcast identifiers of various server functionssuch as DHCP server function, NAT function, ATM-ARP server function,etc., the connection set up address, FA ID or FA address itself of theMobile IP, etc.

(5) Then, the paging channel (PCH) information is periodically receivedby switching to the call termination control channel. At this point, itis also possible to receive the perch channel (dedicated controlchannel) simultaneously, in addition to the call termination controlchannel. It is also possible to receive PCH and BCCH periodically intime division by forming a super-frame.

(6) Also, whether the location registration area number, the radio basestation ID and the MSR ID contained in the received broadcast (BCCH)information are the same as those received until now is judged. If anyof these is different from that received until now, a transition to thelocation registration operation state is made so as to carry out thelocation registration.

Here, when the location registration area number is different, thelocation registration is carried out with respect to a locationregistration register within the mobile communication network via theradio base station.

On the other hand, when the MSR ID is different, the locationregistration is carried out with respect to the MSR via the radio basestation (in order to carry out the location registration to Internettype system). Also, the location registration may be carried out whenthe radio base station ID is different, but the above described twoidentifiers are usually used so as not to make the location registrationtraffic unnecessarily large.

Here, when the MSR has an FA function, it is possible to broadcast theFA address in addition to the MSR ID as the broadcast channel (BCCH)information, and it is also possible to use the FA address as the MSRID.

Moreover, BCCH may be in a configuration in which the CO type systemrelated information for the mobile communication network as well as theCL type system related information for Internet are defined within thesame BCCH channel, or a configuration in which separate logical channelsare defined for the CO type BCCH and the CL type BCCH. In such aconfiguration in which the CO type BCCH (BCCH1) related to the mobilecommunication system and the CL type BCCH (BCCH2) related to Internetare defined separately, BCCH1 is received when the communication usingthe mobile communication network is desired, or BCCH2 is received whenthe Internet communication is desired, and both BCCH1 and BCCH2 arereceived when both types of communications are desired, so that there isa merit in that unnecessary reception can be eliminated.

Also, the terminal that utilizes only a service whose call originatingside is a terminal may have a configuration in which the locationregistration operation for the purpose of realizing the call terminationis unnecessary. However, even in this case, the radio base station ID isto be notified to the network as an own location at a time of callorigination.

(7) When the above described numbers or identifiers are the same asthose received until now, a transition to the standby operation state ismade.

(8) In the standby operation state, when a call origination request isreceived, a transition to the call origination connection operation ismade, whereas when a call termination request is received, a transitionto the call termination connection operation is made.

(9) Also, when the received signal strength of the perch channel(dedicated control channel) drops below the threshold, the operationreturns to the perch channel (dedicated control channel) received signalstrength measurement operation (1). If the received signal strength isnot below the threshold, the operation returns to the operation (8) sothat whether there is a call origination connection request and whetherthere is a call termination connection request are checked repeatedly.

Next, the location registration operation will be described withreferences to FIG. 19 to FIG. 21.

The location registration operation state is an operation state in whichthe current location of the mobile terminal 201 is notified to thenetwork (MSR in this embodiment), and more specifically, the currentlocation of the mobile terminal 201 is notified from the mobile terminal201 to the network by using ACCH (FACCH, SACCH) and/or UACCH (USACCH,UFACCH) defined within USPCH after the random access using SCCH/USCCH,as shown in FIG. 19.

Here, it is possible to use ACCH in the case of CO type communicationand USCCH in the case of CL type communication. The locationregistration operation is carried out when the mobile terminal 201 turnsthe power ON while being within the service area of the MSR, or when themobile terminal 201 enters from outside of zone of the MSR into insidethe service area of the MSR.

In this embodiment, the case of carrying out the location registrationoperation using the MSR ID has been described, but it is also possibleto realize the location registration operation using other identifier orby detecting that the location registration area (LAI) becomesdifferent. Also, in the case of the service mode in which the mobileterminal 201 only originates calls, it is possible to use aconfiguration in which the mobile terminal 201 registers its ownlocation in the call origination connection for the first time, withoutcarrying out the location registration operation.

Next, the location registration operation procedure including thefollowing steps (1) to (4) will be described with reference to FIG. 21.

(1) First, when it is detected the values of the radio base station IDand the MSR ID periodically broadcast from BCCH become different fromthose stored in the memory, a random access using USCCH is made and theradio channel (USPCH) allocation is carried out so as to establish aradio link.

(2) Next, a location registration request message is transmitted to theMSR 220, using ACCH (UACCH) associated with USPCH in the radio sectionand control VC in the wire section. This location registration requestmessage contains the terminal ID of the mobile terminal 201. Theterminal (MS) ID is an information for distinguishing the mobileterminal 201 from the other mobile terminals which is a number assignedwithout any overlap.

In addition to the location information, it is also possible for thelocation registration information to include the connection set upaddress, the PID (Personal ID), the terminal ID, and the base stationID, for the purpose of registering more detailed location information,if necessary.

(3) Upon receiving the location registration request message, the MSR220 registers the terminal (MS) ID in the memory, and notifies alocation registration response message indicating that the locationregistration is completed, using the control VC in the wire section andUACCH in the radio section, to the mobile terminal 201. Also, a requestfor allocation of address such as IP address or ATM address may becontained in the location registration request message or provided bythe location registration request message itself, and a locationregistration response message may contain a part of a whole of thenumbers (IP address, ATM address, etc.) allocated to the mobile terminal201.

(4) After receiving the location registration response message, themobile terminal 202 carries out the disconnection of the radio link(USPCH).

Next, the IP address allocation operation will be described withreferences to FIG. 22 and FIG. 23.

As shown in FIG. 22 and FIG. 23, the IP address allocation operation iscarried out by exchanging an IP address allocation request message andan IP address allocation response message between the address server(DHCP server, which is assumed to be provided in the MSR here) forcarrying out the IP address allocation and the mobile terminal. Anaccess to the address server is made according to the ATM address, theVPI/VCI value, or a part or a whole of the IP address of the DHCP servercontained in the broadcast information. The IP address allocationoperation by the DHCP server will be described in detail below.

Next, the operation of the mobile terminal in the case of carrying outthe call origination connection to the IP terminal within the area ofthe radio base station will be described.

The call origination operation state is an operation state in which,when there is an access request from the mobile terminal 201 to theother terminal (such as the IP terminal 225 or the cellular terminal 227of FIG. 5 for example), the radio channel (TCH) allocation and theconnection setup control message exchange using ACCH are carried outafter the random access using SCCH so as to make it possible tocommunicate with the cellular terminal 227 in the case of CO typecommunication, or the radio channel (USPCH, USCCH) allocation is carriedout after the random access using SCCH so as to make it possible tocommunicate with the IP terminal 225 in the case of CL typecommunication.

Next, the call origination connection operation procedure will bedescribed with references to FIG. 22 and FIG. 23. The call originationconnection operation procedure includes (1) a call origination requestdetection phase, (2) a connection set up phase, (3) an IP addressallocation phase, and (4) an IP packet transfer phase, which areexecuted in an order of (1)→(2), (3)→(4). Either one of (2) and (3) maybe executed before the other, and can be omitted in the case where theallocation is already made at a time of the power ON or locationregistration.

In the call origination connection operation procedure shown in FIG. 22,when a packet transmission request from the mobile terminal 201 occurs,the connection set up operation procedure and the IP address allocationoperation procedure are executed and the IP address of the IP terminal225 is checked by making an access to the DNS (Domain Name System)server for carrying out the name-IP address conversion if necessary, andthe IP packet transfer is carried out. In addition, when the cut-throughtrigger condition is satisfied, the connection set up is carried outonly at one side (FANP) and the switching to a cut-through path is made.

In the call origination connection operation procedure shown in FIG. 23,when a packet transmission request from the mobile terminal 201 occurs,the IP address allocation operation procedure and the connection set upoperation procedure are executed in an order opposite to that of FIG.22, and the IP address of the IP terminal 225 is checked by making anaccess to the DNS server for carrying out the name-IP address conversionif necessary, and the IP packet transfer is carried out. Similarly as inthe case of FIG. 22, when the cut-through trigger condition issatisfied, the connection set up is carried out only at one side (FANP)and the switching to a cut-through path is made.

Also, in the case where the IP address is allocated at a time of thepower ON or the location registration, so that it is already allocatedat a time of the call origination connection operation, the callorigination connection operation procedure of FIG. 23 starts from theconnection set up operation procedure.

Here, the connection set up in FIG. 22 and FIG. 23 can be realized byeither one of the following two configurations (1) and (2).

(1)<<mobile terminal→radio base station→radio CH, radio VCallocation/set up>><<radio base→MSR→wire VC allocation/set up>>

A configuration in which the allocation of radio VC and radio CH and theestablishing of a radio link which are to be set up in the radio sectionbetween the mobile terminal 201 and the radio base station 202 arecarried out by the radio base station 202 upon request from the mobileterminal 201, while the selection of wire PVC or the set up of wire VCto be used in the wire section between the radio base station 202 andthe MSR 220 is carried out by the MSR 220 upon request from the radiobase station 202.

(2)<<mobile terminal→radio base station→radio CH>><<mobileterminal→MSR→radio VC allocation>><<mobile terminal→MSR→wire VCallocation>>

A configuration in which the allocation of radio CH and the establishingof a radio link which are to be set up in the radio section between themobile terminal 201 and the radio base station 202 are carried out bythe radio base station 202 upon request from the mobile terminal 201while the allocation of radio VC is carried out by the MSR 220 uponrequest from the mobile terminal 201, and the selection of wire PVC orthe set up of wire VC to be used in the wire section between the radiobase station 202 and the MSR 220 is carried out by the MSR 220 uponrequest from the radio base station 202.

In these (1) and (2), a method for carrying out the VC allocation andthe radio channel allocation from the request message destination sidewith respect to the request message source side has been described, butthere is also a method for obtaining idle radio VC, idle radio CH, andidle wire VC at the request message source side.

Also, in the connection set up of FIG. 22 and FIG. 23, whether the radiobase station 202 should transmit the wire PVC selection/wire VC set uprequest to the MSR 220 or the mobile communication network 226 isdetermined according to the connection type information which istransmitted by the mobile terminal 201 to the radio base station 202 atthe same as the radio CH and radio VC allocation request is transmitted.

Next, the handoff control in the case where the mobile terminal moveswithin one MSR will be described.

The channel switching during communication (handoff) operation state isan operation state for continuing communication when the mobile terminal201 moves from the radio base station 202 to the radio base station 203,in which the control message exchange is carried out using ACCH and/orSCCH. Here. it is possible to carry out the control message exchange byusing ACCH In the case of CO type communication or USCCH in the case ofCL type communication.

Next, with reference to FIG. 24, one example of the handoff controloperation in the case where the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 will be described.

First, the mobile terminal 201 detects the degradation of the receivedsignal strength or that the radio base station ID (BS#) that isperiodically notified by BCCH becomes different from BS# stored in theinternal memory of the mobile terminal 201, and transmits a handoffrequest message to the MSR 220.

Then, upon receiving the handoff request message from the mobileterminal 201, the MSR 220 carries out the VC connection set up betweenthe MSR 220 and the radio base station 203 according to the radio basestation ID (BS#) of the radio base station 203 that is described withinthat message, while the radio base station 203 establishes a radio linkbetween the mobile terminal 201 and the radio base station 203 andcarries out the radio channel allocation with respect to the mobileterminal 201. Then, using the connection so established, the unicasttransfer is carried out.

Next, with reference to FIG. 25, another example of the handoff controloperation in the case where the mobile terminal 201 moves from the radiobase station 202 to the radio base station 203 will be described.

First, the mobile terminal 201 detects the degradation of the receivedsignal strength, and transmits a handoff request message to the MSR 220.Upon receiving the handoff request message from the mobile terminal 201,the MSR 220 carries out the VC connection set up between the MSR 220 andthe radio base station 203 according to the radio base station ID (BS#)of the radio base station 203 that is described within that message,while the radio base station 203 establishes a radio link between themobile terminal 201 and the radio base station 203 and carries out theradio channel allocation with respect to the mobile terminal 201. Then,the multicast transfer is carried out.

When the received signal strength of the radio base station 203 becomesgood at the mobile terminal 201, the mobile terminal 201 transmits ahandoff completion message to the MSR 220. Then, according to a commandfrom the MSR 220 that received this message, the radio base station 202carries out the radio link release and the VC connection disconnectionand returns to the unicast transfer.

Here, apart from the handoff, it is also possible to use a method inwhich the mobile terminal 201 requests a radio channel to each radiobase station within a range for which the broadcast channel of BCCH canreach, so as to realize the multiple connection with a plurality of basestations, and receives data from all the radio channels corresponding torespective VCs and selects data in the best reception state.

Also, as shown in FIG. 26, the following three methods (1) to (3) areavailable as the multicast transfer method.

(1) A method in which the IP multicast at the IP processing unit onlayer 3 in the MSR is used for the multicast transfer at a time ofhandoff.

(2) A method in which the ATM switch on datalink layer carries out themulticast transfer after the output from the IP processing unit on layer3 in the MSR.

(3) A method in which only the datalink layer switch (ATM) in the MSRcarries out the multicast transfer of some scheme or switches schemesaccording to communication quality.

Next, the concrete example of the table rewriting operation at the radiobase station and the MSR at a time of the handoff operation will bedescribed with references to FIG. 17, FIG. 18 and FIGS. 27 to 29. Also,FIGS. 30 to 35 show various table configurations.

First, the handoff operation in the case of no cut-through transfer willbe described.

The communication system shown in FIG. 17 comprises the mobile terminal201, the radio base stations 202 and 203, the MSR 220, and Internet 224,where the radio section between the mobile terminal 201 and the radiobase stations 202 and 203 has radio channels (radio CH, SVC) set upon-demand and pre-assigned radio channels (radio CH, PVC).

In addition, a Default VC (PVC in which the processing goes up to the IPforwarding processing unit)and a Dedicated VC (individually allocatedPVC or SVC in which the processing can go up to the IP forwardingprocessing unit or can be cut-through transferred at a switch level) areprovided between each one of the radio base stations 202 and 203 and theMSR 220.

Each one of the radio base stations 202 and 203 has a radiochannel-VPI/VCI correspondence management table, for setting the radiochannel and VPI/VCI in correspondence and carrying out VPI/VCIconversion according to the need. In addition, the MSR 220 carries outthe routing processing to determine whether an IP packet received fromInternet 224 should be transferred to the other router or to the radiobase station 202 or 203, and has a routing table having at least a setof destination IP address, Next Hop IP address, and IF number (interfacenumber) to be used for outputting, and an ARP table (connectionmanagement table) capable of at least setting IP address and VCI incorrespondence directly or indirectly.

In this communication system, it is assumed that an IP packet fromInternet 224 is transferred from the MSR 220 via the radio base station202 to the mobile terminal 201. In this case, the following operations(1) to (4) are carried out.

(1) When the IP packet is received from Internet 224, the MSR 220 checkswhether this IP packet is an IP packet destined to this MSR 220 or an IPpacket to be forwarded to next, and forwards this IP packet to the nextIP and interface number corresponding to the destination IP by referringto the routing table if it is not destined to this MSR 220.

(2) Then, VPI/VCI corresponding to the IP address is taken out byreferring to the ARP (connection management) table, and an ATM cell isassembled from the IP packet by attaching the VPI/VCI thereto andtransferred to the radio base station 202.

(3) In addition, at the radio base station 202, the radio channelcorresponding to VPI/VCI of the received ATM cell is taken out from theradio channel-VPI/VCI management table, and a radio packet istransmitted up to the mobile terminal 201 by attaching a radio header,etc., and using the allocated radio channel.

(4) When this radio packet is received, the mobile terminal 201 carriesout the format conversion in the sequence of radio packet→ATMcell→AAL5→IP packet so as to receive the IP packet.

Next, the operation in the case of transition from a state in which theIP packet is transferred through a route of Internet 224→MSR 220→radiobase station 202→mobile terminal 201 to a state in which it istransferred a route of Internet 224→MSR 220→radio base station203→mobile terminal 201 by the handoff will be described with referenceto FIG. 29, which includes the following steps (1) to (7).

(1) When the mobile terminal 201 detects the moving from the radio basestation 202 (1) to the radio base station 203 (2), the mobile terminal201 transmits a handoff request message containing the own terminal ID=A(which may not necessarily be the terminal ID as long as it can uniquelyidentify the terminal) and the base station ID=(2) (which may notnecessarily be the base station ID as long as it can uniquely identifythe visited site location), to the MSR 220, using the pre-assigned radiochannel of the visited site radio base station 203 and the control PVCfor example. (Here, the handoff request message may be notified via theoriginally located site base station, in which case either the commoncontrol channel or the associated control channel may be used.)

(2) Upon receiving this handoff request message, the MSR 220 figures outthe IP address=Y corresponding to the terminal ID=A, and also figuresout the output IF number=4 from the base station ID=(2) (this output IFnumber is the port number of the switch which is different from the IFnumber of the routing table, and indicates a physical IF number incontrast to the IF number of the routing table which indicates a logicaloutput interface which is a management unit of the ARP table), as shownin FIG. 32. Then, a value of VPI/VCI (VPI/VCI=b) is obtained from anidle VPI/VCI management queue provided for each output IF number,according to the figured out output IF number=4. At this point, thetransmission of the figured out IP packet to the old base station isstopped once.

(3) Then, by referring to the ARP table according to the figured out IPaddress, the output IF number=3 and the VPI/VCI value (VPI/VCI=a) forthe originally located site that are registered in the correspondingentry are read out, and this VPI/VCI=a is returned to the idle VPI/VCImanagement queue corresponding to the read out output IF number=3. Inaddition, the output IF number=4 and the VPI/VCI value (VPI/VCI=b) forthe visited site base station that are figured out at the above (2) arewritten into the ARP table.

(4) Then, a VCI/radio CH allocation request (containing VPI/VCI=b andterminal ID=A) is transmitted to the visited site base station 203, soas to request the set up of a radio channel between the mobile terminal201 and the radio base station 203.

(5) Upon receiving this VCI/radio CH allocation request, the radio basestation 203 carries out the operation to set up a radio connectionbetween the mobile terminal 201 and the radio base station 203.

(6) Then, the corresponding value of the radio CH-VPI/VCI correspondencetable is set according to the terminal ID=A or VPI/VCI=b. After that, aVCI/radio CH allocation response (not shown) is returned to the MSR 220.

(7) Upon receiving this VCI/radio CH allocation response (not shown),the MSR 220 restarts the transmission of the IP packet stored in theinternal buffer queue. In this manner, the switching has been realized.

Here, the connection set up between the MSR 220 and the mobile terminal201 that is carried out by the above (4) to (6) may be carried out bythe existing connection set up procedure of Q. 2931, etc., rather thanusing the method for executing the PVC selection as described above.

Also, the order of the ARP table updating of the above (3) and theconnection set up of the above (4) to (6) may be interchanged. In such acase, the restart of the IP packet transmission at the above (7) is tobe carried out according to the fact that the ARP table updating iscompleted.

It is also possible to carry out the handoff processing of there-connection type in which the mobile terminal 201 requests theconnection set up via the visited site base station. In such a case, itis possible to realize the handoff by transmitting a connection set upmessage containing the terminal ID and the visited site base station IDfrom the mobile terminal 201 to the MSR 220 so as to carry out theconnection set up, and carrying out the ARP table updating similarly asdescribed above.

Also, the case of stopping the IP packet transmission during the handoffoperation has been described above, but it is also possible to realizethe handoff in a state of continuing the transmission without stoppingit once, or by a configuration for carrying out the multicast transferusing the ARP table.

Also, in the above (3), there is a need for the operation to return theold VPI/VCI to the idle VPI/VCI management queue, but this may be doneby taking it out from a table for managing the output VPI/VCI valuecorresponding to the input VPI/VCI value (which may be the VPI/VCIconversion table shown in FIG. 29), and returns it to the idle VPI/VCImanagement queue. In such a case, although not shown in the figure,there is a need to store the input VPI/VCI value in addition to the IPaddress value corresponding to the terminal ID in FIG. 32.

Next, the handoff operation in the case of using cut-through transferwill be described with reference to FIG. 18.

The communication system shown in FIG. 18 comprises the mobile terminal201, the radio base stations 202 and 203, the MSR 220, and Internet 224,where the radio section between the mobile terminal 201 and the radiobase stations 202 and 203 has radio channels (radio CH, SVC) set upon-demand and pre-assigned radio channels (radio CH, PVC).

In addition, a Default VC (PVC in which the processing goes up to the IPforwarding processing unit)and a Dedicated VC (individually allocatedPVC or SVC in which the processing can go up to the IP forwardingprocessing unit or can be cut-through transferred at a switch level) areprovided between each one of the radio base stations 202 and 203 and theMSR 220.

Each one of the radio base stations 202 and 203 has a radiochannel-VPI/VCI correspondence management table, for setting the radiochannel and VPI/VCI in correspondence and also carrying out VPI/VCIconversion according to the need. In addition, the MSR 220 carries outthe routing processing to determine whether an IP packet received fromInternet 224 should be transferred to the other router or to the radiobase station 202 or 203, and has a routing table (not shown, see FIG.17) having at least a set of destination IP address, Next Hop IPaddress, and IF number (interface number) to be used for outputting, anARP table (connection management table) capable of at least setting IPaddress and VCI in correspondence directly or indirectly, and a VPI/VCIconversion table for converting input VPI/VCI into output VPI/VCI.

In this communication system, it is assumed that an IP packet fromInternet 224 is transferred from the MSR 220 via the radio base station202 to the mobile terminal 201. In this case, the following operations(1) to (4) are carried out.

(1) When the IP packet is received from Internet 224, the MSR 220 checkswhether this IP packet is an IP packet destined to this MSR 220 or an IPpacket to be forwarded to next, and forwards this IP packet to the nextIP and interface number corresponding to the destination IP by referringto the routing table if it is not destined to this MSR 220.

(2) Then, VPI/VCI corresponding to the IP address is taken out byreferring to the ARP (connection management) table, and an ATM cell isassembled from the IP packet by attaching the VPI/VCI thereto andtransferred to the radio base station 202.

(3) In addition, at the radio base station 202, the radio channelcorresponding to VPI/VCI of the received ATM cell is taken out from theradio channel-VPI/VCI management table, and a radio packet istransmitted up to the mobile terminal 201 by attaching a radio header,etc., and using the allocated radio channel.

(4) When this radio packet is received, the mobile terminal 201 carriesout the format conversion in the sequence of radio packet→ATMcell→AAL5→IP packet so as to receive the IP packet.

Here, when some specific condition such as that the IP packet istransferred for relatively long time, the correspondence in the VPI/VCIconversion table itself is changed and the IP packet is transferred bycutting through the upper level IP forwarding processing unit.

In the following, how this cut-through operation is carried out and howtable change is to be made at that time will be described for the casein which the FANP operation is used only between the MSR and the routerin Internet while the FANP operation is not used and a cut-through isset up between the MSR and the mobile terminal (one side FANPoperation), and for the case in which the FANP operation is used forboth between the MSR and the router in Internet as well as between theMSR and the mobile terminal while cut-throughs in both directions areset up (both side FANP operation), in an exemplary case of transitionfrom the state of FIG. 29 to the state of FIG. 28.

First, the one side FANP operation will be described. Here, in FIG. 29,it is assumed that the mobile terminal is located at the base station(1), and the IP packet communication between the router in Internet andthe mobile terminal is carried out by using the default VC (input VCI=d)that is set up in advance between the router in Internet and the MSR andVCI=a between the MSR and the mobile terminal. In this case, the VPI/VCIconversion table is in a state of having input VCI=d, output VCI=NULLand output IF number=2, while the ARP table is in a state of having nextIP address=Y, base station ID=(1) and output VCI=a.

In this state, when the cut-through trigger condition occurs, the FANPoperation between the router in Internet and the MSR is carried out suchthat the dedicated VC (input VCI=c, output VCI=NULL, output IF number=2)is set up in the VPI/VCI conversion table first, and then a message forsetting this input VCI=c and the IP address=Y in correspondence isexchanged. Then, the VPI/VCI conversion table is updated to the state ofhaving input VCI=c, output VCI=NULL→a and output IF number=2→3, so as torealize the binding of the VPI/VCI conversion table with VCI=a(dedicated VC already set up by signaling and the like) that is used forcommunication between the MSR and the mobile terminal. In this manner,the cut-through transfer as shown in FIG. 28 is realized.

Next, the both side FANP operation will be described. Here, in FIG. 29,it is assumed that the mobile terminal is located at the base station(1), and the IP packet communication between the router in Internet andthe mobile terminal is carried out by using the default VC (input VCI=d)that is set up in advance between the router in Internet and the MSR andVCI=a between the MSR and the mobile terminal. In this case, the VPI/VCIconversion table is in a state of having input VCI=d, output VCI=NULLand output IF number=2, while the ARP table is in a state of having nextIP address=Y, base station ID=(1) and output VCI=a.

In this state, when the cut-through trigger condition occurs, the FANPoperation between the router in Internet and the MSR is carried out suchthat the dedicated VC (input VCI=e, output IF number=2) is set up in theVPI/VCI conversion table first, and then a message for setting thisinput VCI=e and the IP address=Y in correspondence is exchanged.

In addition, the FANP operation between the MSR and the radio basestation or between the MSR and the mobile terminal is activated suchthat the dedicated VC (output VCI=f) is set up between the MSR and theradio base station or between the MSR and the mobile terminal first, andthen a message for setting this VCI=f and the IP address=Y incorrespondence is exchanged.

Then, the VPI/VCI conversion table is updated to a state of having inputVCI=e, output VCI=NULL→f and output IF number=2→3, so as to realize thebinding of the VPI/VCI conversion table with VCI=f that is used forcommunication between the MSR and the mobile terminal and VCI=e that isset up for communication between Internet and the MSR. In this manner,the cut-through transfer as shown in FIG. 28 is realized.

Next, how handoff is realized in this case of cut-through transfer statewill be described. Namely, the operation in the case of transition froma cut-through transfer state in which the IP packet is transferredthrough a route of Internet 224→MSR 220→radio base station 202 o mobileterminal 201 to a state in which it is transferred a route of Internet224→MSR 220→radio base station 203→mobile terminal 201 by the handoffwill be described with reference to FIG. 27, which includes thefollowing steps (1) to (7).

(1) When the mobile terminal 201 detects the moving from the radio basestation 202 (1) to the radio base station 203 (2), the mobile terminal201 transmits a handoff request message containing the own terminal ID=A(which may not necessarily be the terminal ID as long as it can uniquelyidentify the terminal) and the base station ID=(2) (which may notnecessarily be the base station ID as long as it can uniquely identifythe visited site location), to the MSR 220, using the pre-assigned radiochannel of the visited site radio base station 203 and the control PVCfor example. (Here, the handoff request message may be notified via theoriginally located site base station, in which case either the commoncontrol channel or the associated control channel may be used.)

(2) Upon receiving this handoff request message, the MSR 220 figures outthe IP address=Y corresponding to the terminal ID=A, and also figuresout the output IF number=4 from the base station ID=(2) (this output IFnumber is the port number of the switch which is different from the IFnumber of the routing table, and indicates a physical IF number incontrast to the IF number of the routing table which indicates a logicaloutput interface which is a management unit of the ARP table), as shownin FIG. 32. Then, a value of VPI/VCI (VPI/VCI=b) is obtained from anidle VPI/VCI management queue provided for each output IF number,according to the figured out output IF number=4.

Also, although not shown in FIG. 32, the input VPI/VCI valuecorresponding to the terminal ID is also stored besides the IP addresscorresponding to the terminal ID, so that the input VPI/VCI=c is alsofigured out. At this point, the transmission of the figured out IPpacket to the old base station is stopped once.

In the case of using a configuration which does not carry out the ARPtable updating subsequently, the operation to figure out the IP addresscorresponding to the terminal ID is not absolutely necessary. Theoperation to figure out the IP address is also not necessary in the caseof using the fixed IP address instead of the terminal ID.

(3) Then, by referring to the VPI/VCI conversion table according to thefigured out input VPI/VCI (=c), the output VPI/VCI=a and the output IFnumber=3 for the originally located site that are registered in thecorresponding entry are read out, and this VPI/VCI (=a) is returned tothe idle VPI/VCI management queue corresponding to the read out outputIF number=3. In addition, the output IF number=4 and the VPI/VCI value(VPI/VCI=b) for the visited site base station that are figured out atthe above (2) are written into the entry of input VPI/VCI=C.

(4) Then, a VCI/radio CH allocation request (containing VPI/VCI=b andterminal ID=A) is transmitted to the visited site base station 203, soas to request the set up of a radio channel between the mobile terminal201 and the radio base station 203.

(5) Upon receiving this VCI/radio CH allocation request, the radio basestation 203 carries out the operation to set up a radio connectionbetween the mobile terminal 201 and the radio base station 203.

(6) Then, the corresponding value of the radio CH-VPI/VCI correspondencetable is set according to the terminal ID=A or VPI/VCI=b. After that, aVCI/radio CH allocation response (not shown) is returned to the MSR 220.

(7) Upon receiving this VCI/radio CH allocation response (not shown),the MSR 220 restarts the transmission of the IP packet stored in theinternal buffer queue. In this manner, the switching has been realized.

Here, the connection set up between the MSR 220 and the mobile terminal201 that is carried out by the above (4) to (6) may be carried out bythe existing connection set up procedure of Q. 2931, etc., rather thanusing the method for executing the PVC selection as described above.

Also, the order of the VPI/VCI conversion table updating of the above(3) and the connection set up of the above (4) to (6) may beinterchanged. In such a case, the restart of the IP packet transmissionat the above (7) is to be carried out according to the fact that theVPI/VCI conversion table updating is completed.

It is also possible to carry out the handoff processing of there-connection type in which the mobile terminal 201 requests theconnection set up via the visited site base station. In such a case, itis possible to realize the handoff by transmitting a connection set upmessage containing the terminal ID and the visited site base station IDfrom the mobile terminal 201 to the MSR 220 so as to carry out theconnection set up, and carrying out the VPI/VCI conversion tableupdating similarly as described above.

Also, the case of stopping the IP packet transmission during the handoffoperation has been described above, but it is also possible to realizethe handoff in a state of continuing the transmission without stoppingit once, or by a configuration for carrying out the multicast transferusing the VPI/VCI conversion table.

In the above description of the handoff operation at a time of thecut-through transfer, the ARP table updating has not been described but,if the ARP table is set in advance at a time of the switching from thecut-through transfer to the transfer using the usual IP forwardingprocessing, there is a merit in that the switching can be realizedquickly.

For this reason, it is also possible to add the following operation (3)′between the above (3) and (4) of the handoff operation at a time of thecut-through transfer described above.

(3)′ The output IF number=4 and the VPI/VCI value (VPI/VCI=b) for thevisited site base station that are figured out at the above (2) arewritten into the ARP table.

It is also possible to replace the above (3) by the following operation(3)″.

(3)″ By referring to the ARP table according to the figured out IPaddress (=Y), the output IF number=3 and the VPI/VCI value (VPI/VCI=a)for the originally located site that are registered in the correspondingentry are read out, and this VPI/VCI=a is returned to the idle VPI/VCImanagement queue corresponding to the read out output IF number=3.

It is also possible to add the following operation (3)′″ after executingthe ARP table updating processing in which (the output IF number=4 and)the VPI/VCI value (VPI/VCI=b) for the visited site base station that arefigured out at the above (2) are written into the ARP table.

(3)′″ The output IF number=4 and the VPI/VCI value (VPI/VCI=b) for thevisited site base station that are figured out at the above (2) arewritten into the entry of input VPI/VCI=c.

Also, in the handoff operation described above, if the input VPI/VCIvalue is also stored in the entry of the ARP table, there is no need toprovide a table for managing the correspondence between the terminal IDand the Input VPI/VCI (not shown in FIG. 32) at a time of updating theVPI/VCI conversion table after the ARP table updating.

Also, the above description is directed only to an exemplary case ofusing a specific configuration having the ARP table, the VPI/VCIconversion table and the radio channel-VPI/VCI correspondence managementtable, but it is also possible to realize the handoff operation by usingconfiguration of tables as shown in FIG. 33 to FIG. 35, and the presentinvention can be realized by using any of these table configurations.

Next, the case in which the mobile terminal is disconnected within thearea of the radio base station will be described.

The call ending and disconnection operation state is an operation statein which the exchange of control messages related to a disconnection ata time of ending the communication is carried out by using ACCH in thecase of CO type communication or by using USCCH in the case of CL typecommunication, until the communication is ended and disconnected. Here,in the case of CO type communication, the message exchange for the radiochannel release and the wire connection release is carried out at a timeof communication ending, while in the case of CL type communication, themessage exchange for the radio channel release and the release of IPaddress and the like is carried out at a time of communication ending.

Here, the CL type communication implies that the IP packet of the layer3 is connection-less type. Consequently, there is no need for theconnection release when PVC is used for the datalink layer leveltransmission, but there is a need to carry out the connection release ata time of communication ending when the communication was made bycarrying out the connection set up on-demand.

The disconnection operation usually includes a disconnection requestdetection phase and a disconnection execution phase. The disconnectionrequest detection phase is a phase for detecting whether a disconnectionrequest is issued internally or not at the MSR or the mobile terminal201, where the disconnection operation is executed with respect to theopposite side of the connection set up when the disconnection request isissued.

This disconnection operation can be realized by either a network sidedisconnection procedure in which the disconnection procedure isinitiated from the MSR side with respect to the mobile terminal 201, ora terminal side disconnection procedure in which the disconnectionprocedure is initiated from the mobile terminal 201 side with respect tothe MSR.

Now, these two disconnection procedures will be described withreferences to FIGS. 36A and 36B.

FIG. 36A shows the network side disconnection procedure which includesthe following steps (1) to (4).

(1) First, when the timer provided in the connection management table ofthe MSR becomes timeout or an explicit disconnection request is issued,a disconnection (DISC) message is transmitted from the MSR to the mobileterminal 201 by suing the control channel (UACCH, ACCH) associated withthe already set up connection in the radio section and the control VC inthe wire section.

(2) Then, a release (REL) message is transmitted from the mobileterminal 201 to the MSR.

(3) Then, a release completion (REL COMP) message is returned from theMSR to the mobile terminal 201.

(4) Then, the operation is completed by disconnecting the radio linkbetween the radio base station and the mobile terminal 201.

Here, the IP address release operation may be included before or afterthe radio link disconnection operation, and before the disconnectionoperation starts.

FIG. 36B shows the terminal side disconnection procedure which includesthe following steps (1) to (4).

(1) First, when the timer provided in the connection management table ofthe mobile terminal 201 becomes timeout or an explicit disconnectionrequest is issued, a disconnection (DISC) message is transmitted fromthe mobile terminal 201 to the MSR by suing the control channel (UACCH,ACCH) associated with the already set up connection in the radio sectionand the control VC in the wire section.

(2) Then, a release (REL) message is transmitted from the MSR to themobile terminal 201.

(3) Then, a release completion (REL COMP) message is returned from themobile terminal 201 to the MSR.

(4) Then, the operation is completed by disconnecting the radio linkbetween the radio base station and the mobile terminal 201.

Here, similarly as in the case of the network side disconnectionprocedure, the IP address release operation may be included before orafter the radio link disconnection operation, and before thedisconnection operation starts.

When the network side disconnection procedure is executed, the entryupdating of the ARP table (in which at least the IP address and VPI/VCIare set in correspondence) of the MSR that is on the network side isbasically carried out before the execution of the disconnectionprocedure, but it is also possible to carry out this entry updatingafter the execution of the disconnection procedure. It is also possibleto maintain the old connection management table (ARP table) until theset up of a connection to be newly set up is completed in the case wherethe disconnection procedure is carried out at a time of handoffoperation at least.

Next, a method for pausing the transmission at a time of handoff will bedescribed.

The IP packet transmission at a time of handoff can be temporarilystopped while queueing IP packets in an internal buffer. A situation inwhich the handoff request is issued is expected to be a situation inwhich the transfer efficiency is poor and only re-transmission is causedeven when the IP packet transfer to the old connection is attempted,because of the very poor quality in the radio section. In view of thisfact, it is preferable to temporarily stop the IP packet transmissionand store IP packets in the internal queue at a time of handoff, andresume the transmission of IP packets stored in the internal queue whenthe connection set up is completed again.

Considering these points, it is also possible to define a pause state inaddition to a registration state and a cancellation state as the entrystate of the ARP table at a time of handoff. In this case, a packet inthe registration state will be transmitted after being queued, while apacket in the cancellation state will be discarded without being queued,and a packet in the pause state will be queued but not transmitted.

When the IP packet transmission is paused at a time of handoff in thismanner, there is a possibility for influencing the TCP operationdepending on cases. For this reason, it is also possible to provide theMSR with a function for converting TCP in the radio section and TCP inthe wire section. In this case, when a packet is in the pause state asdescribed above, a window size is adjusted (a TCP window size isreduced) so as to lower the transfer rate at the transmitting side.

Next, the operation in the case where there is a call termination fromthe IP terminal at the mobile terminal within the area of the radio basestation will be described.

The call termination operation state is an operation state since anaccess request (calling) is made from the other terminal (the cellularterminal 227 or the IP terminal 225 of FIG. 5, for example) until itbecomes a communication in progress state, in which after being calledby PCH, the radio channel (TCH) allocation and the exchange of controlmessages for connection set up using ACCH are carried out so as to beable to communicate with the cellular terminal 227 in the case of COtype communication, or the own IP address is notified to the IP terminal225 so as to be able to communication with the IP terminal 225 in thecase of CL type communication.

The call termination connection operation includes (1) a calltermination request detection phase, (2) a location check (paging)phase, (3) an address resolution phase, (4) a connection set up phase,and (5) an IP packet transfer phase, which are to be executed in anorder of (1)→(2), (3), (4)→(5).

Here, (2) is an operation for checking the connection target, which maybe executed either simultaneously with or separately from the addressresolution of (3) for the purpose of connection set up. When the valueof VPI/VCI (PVC) that is permanently set up is obtained at a time ofphases (2) and (3), it suffices for the connection set up phases (4) towrite that value into the connection management table without carryingout any signaling operation.

Next, with references to FIG. 37 and FIG. 38, the call terminationconnection operation will be described. The call termination connectionoperation procedure shown in FIG. 37 is an operation procedure in whichthe MSR 220 carries out the location check operation procedure based onreceiving of an IP packet from the IP terminal 225, and then theconnection set up operation procedure is carried out from the mobileterminal 201 so as to carry out the IP packet communication and the IPpacket cut-through transfer. The call termination connection operationprocedure shown in FIG. 38 is an operation procedure in which the MSR220 carries out the location check operation procedure based onreceiving of an IP packet from the IP terminal 225, and then theconnection set up operation procedure is carried out from the MSR 220 soas to carry out the IP packet communication and the IP packetcut-through transfer.

Here, in the connection set up in FIG. 37 and FIG. 38, the operationbecomes different depending on which one of the mobile terminal 201, theradio base station 202, and the MSR 220 is going to be an entity formanaging the setting of the wire section to be either one of (PVCselection, SVC allocation) and the setting of the radio section to beany one of (on-demand radio CH allocation, pre-assigned radio CHselection) and (radio PVC selection, radio SVC allocation), but the calltermination operation can be realized in any of these configurations.

Also, the connection set up of FIGS. 22 and 23 and FIGS. 37 and 38 canbe realized by utilizing the existing connection set up procedure suchas Q. 2931, etc.

Also, the IP address allocation of FIGS. 22 and 23 can be realized byutilizing the existing IP address allocation set up procedure such asDHCP, etc.

Here, the location check operation procedure of FIGS. 37 and 38described above is activated when a subnet ID field of the destinationIP address of the received IP packet coincides with a subnet of the MSR220, and derives the terminal ID from the IP address and carries out thepaging operation similar to that of the mobile communication accordingto that terminal ID, where upon receiving this paging request, themobile terminal 201 returns a paging response to the MSR 220. Then, theMSR 220 checks the location of the mobile terminal 201 according to theterminal identifier (terminal ID) and the radio base station identifier(radio base station ID) contained within that paging response.

Also, the location check operation procedure of FIGS. 37 and 38described above is activated when a subnet ID field of the destinationIP address of the received IP packet coincides with a subnet of the MSR220, and derives the terminal ID from the IP address and carries out thepaging operation similar to that of the mobile communication accordingto that terminal ID, where the location check operation procedure iscarried out by the operation procedure similar to that of ARP byresolving (terminal ID, radio base station ID) corresponding to the IPaddress. Namely, the location check is carried out in such a manner thatan ARP request packet from is transmitted from the MSR 220, and uponreceiving this ARP request packet the mobile terminal 201 returns an ARPresponse packet containing the terminal ID and the radio base station IDto the MSR 220.

Next, the detailed configuration of the MSR will be described withreference to FIG. 39.

As shown in FIG. 39, the MSR is a router device comprising a controlunit 310 and a switch unit 311, where the control unit 310 has at leastan IP forwarding function 300, a location management (MM) function 301,a network layer address allocation function (DHCP function) 302, and acut-through path set up/release function 303. Here, the switch unit 311may not necessarily be an ATM switch, but in the following descriptionit is assumed that the switch unit 311 is formed by an ATM switch.

The location management (MM) function 301 is formed by a locationinformation memory module 320 and a location update module 321. The DHCPfunction 302 is formed by an address allocation memory module 322 and anaddress allocation change module 323. The switch unit 311 is formed by atransfer target memory module 324 and a transfer target determiningmodule 325.

In this embodiment, the MSR has the following characteristics.

(1) The MSR differs from (conventional router device+mobile accesstechnique) in that, when the mobile terminal 201 moves between the radiobase stations 202 and 203, the location movement management function ofthe MSR detects the moving of that mobile terminal 201 (by receiving amoving notice from any of the mobile terminal 201 and the radio basestations 202 and 203 and detecting the received notice), and thedatalink layer switch unit (such as Ethernet switch, ATM switch, etc.)carries out the switching of the transfer route at the datalink level,so as to be able to realize the handoff faster than the conventionalhandoff technique on the network layer level used in the Internet typenetwork.

(2) The MSR also differs from (conventional router device+mobile accesstechnique) in that, when the mobile terminal 201 moves between the radiobase stations 202 and 203, the location movement management function ofthe MSR detects the moving of that mobile terminal 201 (by receiving amoving notice from any of the mobile terminal 201 and the radio basestations 202 and 203 and detecting the received notice), and theinstantaneous disconnection of the communication is eliminated byrealizing the multiple connection at the MSR, in contrast to(conventional router device+mobile access technique) in which thecommunication is disconnected and then re-connected after the mobileterminal 201 has moved to the visited site radio base station 203, so asto be able to realize the handoff with superior communication qualitythan the conventional handoff technique used In the Internet typenetwork.

Also, by additionally storing the correspondence with respect to theservice quality information (traffic type (such as media type),connection type, terminal type) in the transfer target memory module324, the transfer target determining module 325 can easily switch amongthe datalink layer level transfer, the network layer level transfer, theunicast transfer, and the multicast transfer, according to the servicequality stored in the transfer target memory module 324, on the basis ofthe table entry contents and the above characteristics (1) and (2).

Also, as a method of multiple connection, a method for carrying out themulticast transfer (such as IP packet multicast, for example) on thenetwork layer level and a method for carrying out the multicast transfer(such as ATM cell multicast, for example) on the datalink layer levelare available. When combined with the layer 3 switch, even the multipleconnection on the network layer level can be expected to improve theperformance significantly, but the performance can be even better in themultiple connection on the datalink layer level.

In addition, in the radio communication system of CDMA scheme, the MSRcan make use of the features of the CDMA scheme in the case where themulticast transfer is indispensable in order to realize the softhandoff. Also, by providing a server (provided at a location of gateway,for example) which has centralized location management function asdescribed above, the high speed and high quality handoff can besupported even for the handoff over MSRs.

Here, it is also possible to use a combination with the conventionalmobile access technique such as Mobile IP for the handoff over MSRs.Namely, for the local handoff control within the MSR, the locationmovement management function is provided in the MSR and thecommunication channel switching type or re-connection type handoffcontrol is carried out on the datalink layer level (such as ATM level),whereas the conventional re-connection type mobile access technique isused for the handoff over MSRs.

When the MSR of the present invention is combined with the existingtechnique in this manner, there is a demerit in that the communicationwill be temporarily disconnected at a time of the handoff between MSRsfor a time longer than the handoff on the datalink layer level, butthere is a merit that the service area can be enlarged.

Next, with reference to FIG. 39, each function block and interfacebetween functional modules of the MSR will be described.

As shown in FIG. 39, the MSR comprises the switch unit 311 and thecontrol unit 310, where the switch unit 311 and the control unit 310 isconnected by input/output ports 51 in which the default VC and thecontrol VC are set up.

The switch unit 311 is formed by the transfer target determining module325 and the transfer target memory module 324. The transfer targetdetermining module 325 has input ports 21 to 2N and output port 11 to 1Nas the external connection interfaces of the MSR, while the input/outputports 51 for the control VC and the default VC and a VPI/VCI managementtable changing interface 31 as connection interfaces with respect to thecontrol unit 310 of the MSR, and an internal connection interface 50between the transfer target determining module 325 and the transfertarget memory module (VPI/VCI management table) 324 within the switchunit 311. This transfer target determining module 325 has an exchangefunction for reading out an output port by making an access to thetransfer target memory module 324 according to VPI/VCI of an ATM cellentered from some port, and outputting the ATM cell to that output port.In the case where a plurality of output ports are specified in thetransfer target memory module 324, it also has a function for carryingout the multicast transfer of the ATM cell.

The transfer target memory module 324 is a table for managingcorrespondence among input VPI/VCI, output VPI/VCI, and output portnumber, which has a cut-through path set up/release function 303 and aconnection interface with respect to the transfer target determiningmodule 325, and carries out read/write of output VPI/VCI information,output port number, etc., by making access to entry according to inputVPI/VCI.

Here, the ATM cell entered from the input ports 21 to 2N of the switchunit 311 is received by preliminary processing unit provided at eachinput port of the transfer target determining module 325, and an accessto the transfer target memory module 324 is made according to VPI/VCI ofthe ATM cell header. Then, the ATM cell is outputted to a desired outputport by a switch inside the transfer target determining module 325according to the output port number described in an accessed entry. Atthis point, when the entered ATM cell is a control information, it isoutputted to the input/output ports 51, whereas when it is a userinformation, it is outputted to the output ports 11 to 1N.

Also, the ATM cell entered from the input/output ports 51 is similarlyreceived by the preliminary processing unit provided at eachinput/output port, and outputted to a desired output port by the switchinside the transfer target determining module 325 according to theoutput port number described in an entry accessed by referring to thetransfer target memory module 324.

The control unit 310 is formed at least by the location managementfunction 301, the network layer address allocation function 302, thecut-through path set up/release function 303 and the IP forwardingfunction 300.

The IP forwarding function 300 is a functional block for carrying outthe IP packet processing as carried out by the usual router device,which analyzes the IP packet and executes either one of the followingtwo operations.

(1) If the IP packet is destined to this MSR, the packet is given to thenetwork layer address allocation function 302, the location managementfunction 301 and the cut-through path set up/release function 303through interfaces 41, 42 and 43, respectively.

(2) If the IP packet is not destined to this MSR, an output port to arouter device (or a terminal) to which it should be outputted next isdetermined by referring to the routing table, and outputted to thedefault VC of the input/output port again after converting it back tothe ATM cell.

Also, the network layer address allocation function 302 is formed by theaddress allocation change module 323 and the address allocation memorymodule 322. The address allocation change module 323 carries out eitherone of the following two operations according to a message of the IPpacket received from the IP forwarding function 300.

(1) If the message is an IP address allocation request from the mobileterminal 201, an IP address is taken out from the idle IP addressmanagement queue according to this IP address allocation request, andthen an access to the address allocation memory module 322 is madeaccording to the taken out IP address and the terminal ID is stored intothe accessed entry. Then, an address allocation response messagecontaining the taken out IP address is converted into an IP packet andoutputted to the IP forwarding function 300.

(2) If the message is an IP address release request from the mobileterminal 201, an access to the address allocation memory module 322 ismade according to that IP address and the terminal ID described thereinis deleted, while that IP address is stored Into the idle IP addressmanagement queue. Then, an IP address release response message isconverted into an IP packet and outputted to the IP forwarding function300.

Note that the general description has been given here but it is alsopossible to use the DHCP function for this IP address allocation.

The cut-through path set up/release function 303 is connected with thetransfer target memory module 324, the location management function 301,the transfer target determining module 325 (and/or the IP forwardingfunction 300) through signal lines 31, 36, 34 (and/or 43), respectively.

The cut-through path set up/release function 303 makes an access to thetransfer target memory module 324 through a signal line 31, and switchesthe transfer target determining module (switch) routing path by carryingout read/write of the output port value corresponding to VPI/VCI. Thispath setting switching operation is carried out as the cut-through pathset up/release function 303 receives a switching trigger signal from thelocation management function 301 requesting the switching of(point-to-point connection→multicast connection) or (multicastconnection→point-to-point connection).

Also, the IP packet entered from the input/output port 51 (default VC)and processed by the IP forwarding function 300 is analyzed, and when aswitching trigger for the cut-through path setting occurs, the switchingfrom the VC setting for passing through the IP forwarding function 300to the VC setting for by-passing to the transfer target determiningmodule 325 is made.

Also, when the switching trigger for release occurs, the VC release iscarried out. The VC release is carried out either according to the timeror by taking the handoff as a trigger.

The location management function 301 is formed by a location updatemodule 321 and a location information memory module 320, and carries outthe exchange of information with the transfer target determining module325, the cut-through path set up/release function 303 and the IPforwarding function 300 through signal lines 32, 36 and 42,respectively. The location update module 321 analyzes the IP packet orthe ATM cell received from the IP forwarding function 300 or thetransfer target determining unit 325, and upon receiving a locationregistration message, updates the content (a set of a part or a whole ofterminal ID, radio base station ID, IP address, VPI/VCI, output IFnumber, physical address, etc.) of the location information memorymodule 320 and sends a response to the mobile terminal 201 through thecontrol VC.

Also, when there is a call termination request with respect to themobile terminal 201, the access to the location information memorymodule 320 is made and when the registered entry is found, a messagecontaining the terminal ID of the mobile terminal 201 is notifies to theradio base station, and the paging is carried out by using PCH. If noregistered entry is found, it implies that the mobile terminal does notexist within the MSR, so that the paging is not carried out.

The location information memory module 320 stores a set of (a part or awhole of terminal ID, radio base station ID, IP address, VPI/VCI, outputIF number, physical address, etc.), where the entry content is writtenby being accessed from the location update module 321. The entryupdating is carried out at times of the location registration, thehandoff control, the address allocation/release, etc.

At a time of the location registration, at least the terminal ID (andmay be also the radio base station ID) is registered, and theregistration/updating of the correspondence among (a part or a whole ofa set of terminal ID, radio base station ID, IP address, VPI/VCI, outputIF number, physical address, etc.).

At a time of handoff control and at a time of addressallocation/release, the registration/updating of the correspondenceamong (a part or a whole of a set of terminal ID, radio base station ID,IP address, VPI/VCI, output IF number, physical address, etc.) iscarried out. For example, this updating operation is done by aconfiguration of the location information memory module as shown in FIG.32. Namely, according to the terminal ID information contained withinthe handoff request message from the mobile terminal, the correspondingIP address=Y is figured out, and according to the visited site basestation ID=(2), the output IF number=4 corresponding to that basestation is figured out. Then, the VPI/VCI value is obtained from theidle VPI/VCI management queue (for #4) provided for each IF numberaccording to the figured out output IF number #4, and the updating ofthe IF number of the location information memory module (ARP table) =3→4and VPI/VCI=a→b is carried out.

Also, as shown in FIG. 32, when the ARP table is formed by terminal ID,IF number (base station ID) and VPI/VCI, upon receiving the handoffrequest message, the IF number is changed by using the terminal IDcontained within the handoff request message as a key, while VPI/VCI=bis obtained from the idle VPI/VCI management queue (#4) corresponding tothe received IF number (base station ID) and the change of VPI/VCI=a→bis made.

Also, the location management function 301 and the network layer addressallocation function 302 may be placed on the upper layer of the IPforwarding function 300, or on the upper layer of the AAL layer. (It isalso possible to place them on the lower layer of or the same layer asthe IP forwarding function 300.)

Also, FIG. 40 shows a configuration of the transfer target memory module324. As shown in FIG. 40, the transfer target memory module 324 has anentry of information such as media type, etc. By switching the transfermethod according to the media type on a basis of a transfer targetchange module provided within the cut-through path set up/releasefunction 303, there is a merit in that it is possible to realize thepath switching according to the requested quality of the communication.

Also, when the preliminary processing unit of the switch unit refers tothe transfer target memory module 324 and transfers the service qualityinformation of this media attribute information, etc. in addition to therouting information, etc., to the transfer target determining module325, it can be used for the priority control within the transfer targetdetermining module 325.

Next, with reference to FIG. 41, the radio base station will bedescribed in detail.

FIG. 41 shows a configuration of each one of the radio base stations202, 203, 210 and 211. The radio base station shown in FIG. 41 comprisesan amplifier unit (for transmission and reception), a radio unit, abaseband signal processing unit, a channel processing unit, atransmission path interface, and a radio base station control unit.

Also. FIG. 42 to FIG. 44 show exemplary internal configurations of thetransmission interface that has a unit for multiplexing/demultiplexingCO type communication and CL type communication, VPI/VCI conversiontables, VPI/VCI management tables (tables for managing correspondencebetween radio CH and VPI/VCI), etc. In addition, FIG. 35 shows exemplaryconfigurations of a VPI/VCI management table (radio CH-VPI/VCIcorrespondence management table).

As shown in FIG. 35, there are various possible configurations for theVPI/VCI management table (radio CH-VPI/VCI correspondence managementtable), and when the allocation of the radio channel or radio VC, thePVC selection in the wire section, and the VPI/VCI allocation arecarried out, the updating of the VPI/VCI management table (radioCH-VPI/VCI correspondence management table) shown in FIGS. 42 to 44 iscarried out.

This updating of the radio CH-VPI/VCI correspondence management table iscarried out at times of the call origination connection operation, thecall termination connection operation, the handoff control operation,etc., as described above.

Also, FIG. 34 shows exemplary configurations of a VPI/VCI conversiontable. Here, in the case of conversion of VPI/VCI used in the radiosection and VPI/VCI used in the wire section where the connection typeinformation is not existing in the entry of the VPI/VCI managementtable, the connection type information is provided in this VPI/VCIconversion table.

This is the same configuration as that of the VPI/VCI management tableof the MSR described above, and the configurations of the VPI/VCIconversion table shown In FIG. 34 can be used for the VPI/VCI managementtable of the MSR as well.

In addition, the interface among the radio base station control unit,the channel processing unit, and the transmission interface has aconfiguration as shown in FIG. 45. Namely, at the channel processingunit (CH), the logical channel information as defined in FIG. 6 isseparated into the control channel information to be transferred to theradio base station control unit (BS-CNT) and the user information to betransferred to the transmission interface (INT), and the above describedchannel information is multiplexed according to the need in the case ofreceiving information from the network side.

Next, how the logical functions are mapped to physical structureelements of the communication system shown in FIG. 5 and the moving overthe MSRs (moving over subnets in the case where the MSR constitutes asingle subnet) will be described. Here, the mobility support in the caseof moving over subnets and the system operation in the case of an accessto the private IP network or an access to the global IP network will bemainly described for exemplary functional arrangements shown in FIG. 46to FIG. 50.

The functional arrangement of FIG. 46 comprises the mobile terminal 201,the radio base stations 202, 203, 210 and 211, the MSRs 220 and 221, thegateway 223, Internet 224, and a router 229 of the home network 228. Themobile terminal 201 has the location movement management (MM1 or MM2)function, the network layer address allocation/release (such as DHCPclient) function, the call control (CC) function, and the radiomanagement (RT) function, without having any function related to theMobile IP. Each of the radio base stations 202, 203, 210 and 211 has thelocation movement management (MM) function, the call control (CC)function, and the radio management (RT) function at least. The MSR hasthe location movement management (MM) function, the network layeraddress allocation/release (such as DHCP server) function, the callcontrol (CC) function, the switch control (SWC) function, and thecut-through path set up/release (such as FANP) function, without havingany function related to the Mobile IP.

Here, the DHCP server described above carries out the message exchangewith the DHCP client, so as to carry out the private IP addressallocation.

Also, the gateway 223 has the address conversion (NAT) function, thelocation movement management (MM) function, the call control (CC)function, the switch control (SWC) function, and the cut-through pathset up/release (such as FANP) function at least.

The private IP network is provided between the gateway 223 and the MSRs220 and 221 described above, and the routing by the exchange at thedatalink layer level is to be carried out between the MSR 220 and theradio base stations 202 and 203, between the MSR 221 and the radio basestations 210 and 211, and between the radio base stations 202, 203, 210and 211 and the mobile terminal 201. Each of the MSRs 220 and 221 shownin FIG. 46 constitutes a single subnet, and has a configuration usingthe DHCP server function for the private network, while the gateway hasthe address conversion function (NAT) so that the DHCP function and theNAT function are provided at separate locations.

In the case of FIG. 46, when the mobile terminal 201 makes an access tothe server and the like within the private IP network, the private IPaddress is temporarily allocated by the DHCP server function provided atthe MSR 221, and the service is provided by making an access to the WWWserver or the mail server within the private IP network by using thisallocated private IP address. At this point, the IP addresses of thevarious servers such as the WWW server and the mail server and thedefault VC (PVC) value may be contained as a part of the broadcastchannel information that is periodically transmitted from the radio basestation, or may be obtained by the service resolution protocol forresolving the location of the server, etc.

Here, the service resolution protocol is a protocol for resolving the IPaddress of the server which can realize the service content, where theresolution can be realized by returning a service resolution response IPpacket in response to the transmission of a service resolution requestIP packet containing the service ID (server ID). (Here it is notabsolutely necessary for the service resolution request and responsemessages to be IP packets).

At the time of service access, either one of the following two methodswill be used.

(1) A method for transmitting IP packets by utilizing the default VC(PVC) network.

(2) A method for transmitting IP packets by setting up a dedicated VC(SVC) (carrying out the connection set up).

As a method for carrying out the connection set up, the connection setup may be carried out for either one or both of the connection betweenthe mobile terminal and the MSR and the connection between the MSR andthe server (or the other MSR).

Also, when the mobile terminal 201 moves over subnets during the accessto the server within the private IP network, either one of the followingtwo methods will be used.

(1) A method for carrying out the IP address re-allocation.

(2) A method for maintaining the initially allocated IP address.

The method (1) for carrying out the IP address re-allocation is a methodin which the session to the WWW server Is set up again automaticallywhen the IP address is obtained again after the moving (a method inwhich the access is made again).

The method (2) for maintaining the initially allocated IP address has amerit in that the session is maintained even through it is disconnectedonce at the datalink layer level. This corresponds to a state in whichthe subnet is virtually extended, where a new call termination duringthe communication is handled in such a manner that the call terminationto the subnet at which the IP address is initially obtained is madefirst, and then the call termination is subsequently made through theconnection route which is connected at the datalink level. In the MobileIP like expression, the place where the IP address is obtained initiallybecomes the home network, and thereafter the VPI/VCI connection isextended in conjunction with the moving as the connection set up betweenthe MSRs of the originally located site and the visited site is carriedout at the visited site in conjunction with the moving over the MSRs.

In this case, it is preferable to also count the number of moving hopsbetween the MSRs, and to set up a connection with respect to the homeMSR again so as to optimize the route when the counted hop numberbecomes greater than a certain value.

Namely, when the moving over subnets is made, the connection is set upfrom the visited site MSR with respect to the originally located siteMSR by exchanging moving information between the MSRs, so as to realizethe routing that appears to extend the subnet as described above. Thisis the operation to be carried out in order to secure the calltermination route for the mobile terminal.

In this case, it suffices for the mobile terminal itself to carry outthe operation to notify the ID of the originally located site MSR or theconnection set up address such as ATM address to the visited site MSR.

Next, with reference to FIG. 48, the handoff control operation in thecase of moving over MSRs will be described.

The radio communication system shown in FIG. 48 comprises the MSRs 220and 221, the radio base stations 202, 203, 210 and 211, and the mobileterminal 201, where the MSR 221 has a routing table for managing acorrespondence among destination IP, next IP and IF number, and an ARPtable for managing a correspondence between IP address and VPI/VCI, aswell as a VPI/VCI conversion table, and each of the radio base station202, 203, 210 and 211 has a VPI/VCI-radio channel management table.

Also, in the radio communication system of FIG. 48, at least a defaultVC (PVC) which is a VC to be utilized as a shared channel that is set upin advance is defined between the MSR and the radio base station, and atleast a pre-assigned radio channel (PVC) which is a radio channel thatis set up in advance is defined between the radio base station and themobile terminal. In addition, the control channel B as defined above andthe communication channel are set up in advance in the manner of(configuration 4) of FIG. 7, and it is assumed that at least the basestation ID (IF number), a PVC of the control channel B {a set of (radioCH, VPI/VCI)}, a PVC of the communication channel {a set of (radio CH,VPI/VCI)}, and a subnet (MSR) ID are notified from each radio basestation.

Now, for the case in which the mobile terminal 201 moves from the radiobase station 210 to the radio base station 203, the procedure forswitching from a state in which the IP packet communication withInternet 224 is carried out by using PVC1 to a state in which the IPpacket communication with Internet 224 is to be carried out by usingPVC2 will be described.

First, the mobile terminal 201 detects the moving over subnets from theradio base station 210 to the radio base station 203 by the fact thatthe base station ID that is periodically notified from the radio basestation has changed, and that the subnet ID (MSR ID) has changed. Then,the mobile terminal 201 notifies a handoff request message containingthe IP address=Y of the mobile terminal 201, VPI/VCI−b of PVC2, thesubnet ID=Aa of the originally located site MSR (and the base stationID=#4 if necessary) to the MSR 220, using the control channel B of theradio base station 203 which is the radio base station used after themoving.

Upon receiving this handoff request message, the MSR 220 updates theconnection management table (ARP table) shown in FIG. 48 according tothe IP address=Y and VPI/VCI=b contained within this handoff requestmessage. Also, the MSR 220 sets up VCI=d by carrying out the connectionset up of the PVC selection with respect to the originally located siteMSR 221, and transmits a routing change request message containing atleast the IP address=Y of the mobile terminal 201 and VPI/VCI=d to theMSR 221. In addition, the MSR 220 sets up VCI=b and the output IFnumber=#4 contained within the handoff request message into the entry ofinput VCI=d that is selected or set up above in the VPI/VCI conversiontable.

Upon receiving the routing change request message, the MSR 221 updatesthe ARP table 511 by changing VPI/VCI=a→d according to the IP address=Yof the mobile terminal 201 and VCI=d that is set up between the MSRs ascontained within the routing change request message.

This completes the handoff control operation, so that the IP packetcommunication between Internet 224 and the mobile terminal 201 isswitched from a communication using PVC1 to a communication using PVC2and VCI=d.

In addition, it is also possible to transmit a routing change responsemessage (which contains information contained in the routing changerequest message such as the IP address=Y of the mobile terminal 201 andVPI/VCI=d) as a response message to the routing change request messagefrom the MSR 221 to the MSR 220, so as to indicate the completion of therouting change explicitly.

In addition, in the case where the MSR 220 explicitly notifies thehandoff completion to the mobile terminal 201 and the mobile terminal201 carries out the switching to the restart of the IP packettransmission from the mobile terminal 201 to Internet 224 by using thishandoff completion (handoff request response) message as a trigger, theMSR 220 may transmit a handoff completion message (which containsinformation contained in the handoff request message such as the IPaddress=Y, the base station ID=#2, and VPI/VCI=b) to the mobile terminal201, using the control channel B. Here, the MSR 220 may transmit thehandoff completion (request response) message to the mobile terminalafter receiving the routing change response message.

Also, when the handoff request message and the routing change requestmessage contain the connection set up address of the visited site MSR220 or the connection set up address (telephone number, ATM address,etc.) of the mobile terminal 201, it is also possible to carry out theupdating of the VPI/VCI conversion table 501 and the updating of the ARPtable 511 by the method for setting up a connection from the originallylocated site MSR to the mobile terminal 201. It is also possible tocarry out the updating of the VPI/VCI conversion table 501 and the ARPtable 511 by the method for setting up a connection from the mobileterminal 201 to the originally located site MSR and then notifying ahandoff request containing the IP address=Y of the mobile terminal 201to the originally located site MSR.

In the following, the scheme described above will be referred to as avirtual subnet scheme. This scheme is based on the fact that, by theexchange of the routing change messages between the MSRs, the datalinklevel connection is extended in the state of maintaining the IP addressof the area at which the IP address is initially obtained even in thecase of moving over subnets, so that it is possible to process as if thesubnet is extended.

As described above, the access to the server within the private IPnetwork can be realized by the following two methods.

(1) A method for transmitting IP packets by utilizing the default VC(PVC) network.

(2) A method for transmitting IP packets by setting up a dedicated VC(SVC) (carrying out the connection set up).

Also, the case in which the mobile terminal 201 moves over subnetsduring the access to the server within the private IP network can berealized by the following two methods.

(1) A method for carrying out the IP address re-allocation.

(2) A method for maintaining the initially allocated IP address.

By combining these methods, it becomes possible to make an access to theserver even when the mobile terminal moves over subnets.

In the case of FIG. 46, when the mobile terminal 201 makes an access tothe mobile terminal (not shown) within the other private IP network (notshown), if that mobile terminal (not shown) exists within the MSR 221,it is possible to carry out the communication by calling that mobileterminal and call terminating by the location movement management (MM)function of the MSR. In contrast, when the mobile terminal (not shown)exists at a location over subnets, the MSR 221 cannot call that mobileterminal. In such a case, there is a need to provide a function forresolving the location/address of the mobile terminal indicating inwhich MSR the mobile terminal is existing.

Next, the operation procedure in the case where the mobile terminal 201carries out the communication with the mobile terminal within the samesubnet will be described. As described below, the operation procedurecan use a method for utilizing the default VC network and a method forutilizing the dedicated VC network, and it is preferable to change whichone of these methods is to be selected according to the application. Theformer method can be applied to the UBR and ABR services of the ATM,while the latter method can be applied to the CBR, VBR and ABR servicesof the ATM.

As an example, the case of resolving address by a method in which thedefault VC (PVC) network is utilized and the conventional RARP frameworkis partially expanded will be described.

(1) The call originating side mobile terminal 201 checks whether the IPaddress corresponding to the call terminating side terminal ID exists inthe own ARP table (cache).

(2) When the IP address corresponding to the call terminating sideterminal ID exists in the ARP table of the call originating side mobileterminal 201 and it is not yet in a state of IP packet communication inprogress (i.e., it is in a state of not communicating), a callorigination request IP packet (containing the call terminating sideterminal ID, the call originating side terminal ID, and the IP addressof the call originating side terminal) is transmitted to the callterminating side mobile terminal. When the IP address corresponding tothe call terminating side terminal ID exists in the ARP table of thecall originating side mobile terminal 201 and it is already in a stateof IP packet communication in progress, the IP packet is transmitted tothe call terminating side mobile terminal. When the IP addresscorresponding to the call terminating side terminal ID does not exist inthe ARP table of the call originating side mobile terminal 201, thetransition to the RARP operation of (5) described below is made.

(3) Upon receiving this call origination request IP packet, the callterminating side mobile terminal checks whether the terminal IDcontained in the call origination request IP packet coincides with theown terminal ID or not, and if it is destined to this mobile terminal,an ACK response IP packet is returned (it is also possible to return aNACK response IP packet when it is not destined to this mobileterminal).

(4) When this ACK response IP packet is received by the call originatingside mobile terminal, the IP packet communication starts. After the IPpacket communication starts, the transition to the RARP operation of (5)is made by the call originating side mobile terminal when the NACKresponse IP packet is received or the timer set at a time of the callorigination request IP packet transmission becomes timeout.

(5) The call originating side mobile terminal executes the RARPoperation so as to resolve the call terminating side IP addresscorresponding to the call terminating side terminal ID.

(6) The call terminating side IP address corresponding to the callterminating side terminal ID is obtained by this RARP operation,registered into the entry of the ARP cache, and its state is set to bethe communication in progress state or the not communicating state, andthen the operation returns to (2) described above.

Here, when the state is set to be the not communicating state here, theoperation to start the IP packet transmission will not be carried outimmediately in (2) described above, but it serves as a function forchecking again because there is a possibility for the IP address to bechanged in conjunction with the moving, after the RARP operation. Inview of these factors, it is preferable to realize the IP addressallocation by the DHCP server in such a manner that the IP address isallocated sequentially from an IP address for which the time of beingnot allocated is longer.

Here, the RARP operation can be realized by a method for using the RARPserver and a method for executing the RARP operation between terminals,and either method may be used. The method for directly executing theRARP operation between terminals may be limited for the use within thesame subnet, or may be allowed for the use over subnets. However, whenthe broadcast is utilized similarly as the conventional RARP, theconventionally noted drawback due to the waste of bandwidth caused bythe broadcast will occur so that it is preferable to use the RARPserver.

The RARP server function is preferably provided within the same deviceas the DHCP server function at which the latest information isavailable. FOr example, it is possible to provide the RARP serverfunction and the DHCP server function in the MSR.

Also, when it becomes unavoidable to change the IP address during thecommunication, it is also possible to use a method in which the exchangeof the registration request IP packet (which contains at least theterminal ID and the new IP address) and the registration response IPpacket (which contains at least the terminal ID and the new IP addressas contained in the registration request IP packet) is carried outbetween the mobile terminals in communication so as to confirm thechange of the IP address.

Also, when it becomes unavoidable to change the IP address during thecommunication, it is also possible to use a method in which thecommunication disconnection is detected by the timeout and the like andthe procedure of (1) to (6) described above is executed again.

Also, it is also possible to use a configuration in which theregistration request IP packet is exchanged between the MSRs when the IPaddress allocation/release occurs at the DHCP server, so that each MSRcan always comprehend a set of (terminal ID, IP address) in an activestate. It is also possible to use a method in which (2) to (4) describedabove are realized without using the RARP expanded operation.

Next, an exemplary case of a method for transmitting IP packets bysetting up a dedicated VC (SVC) (carrying out the connection set up)will be described.

(1) The call originating side mobile terminal 201 checks whether theconnection set up address (such as ATM address) and VPI/VCIcorresponding to the call terminating side terminal ID exist in the ownARP table (cache).

(2) When the connection set up address corresponding to the callterminating side terminal ID exists in the ARP table of the calloriginating side mobile terminal 201 and its VPI/VCI also exists, thetransition to the operation of the above described method in which thedefault VC (PVC) network is used and the framework of the conventionalRARP is partially expanded, starting from the step (1), is made. Whenthe connection set up address corresponding to the call terminating sideterminal ID exists in the ARP table of the call originating side mobileterminal 201 and its VPI/VCI does not exist, the connection is set upaccording to that connection set up address and VPI/VCI is registeredinto an entry corresponding to the call terminating side terminal ID inthe ARP table, and the transition to the operation of the abovedescribed method in which the default VC (PVC) network is used and theframework of the conventional RARP is partially expanded, starting fromthe step (1), is made.

The connection set up at this point may be realized by the existingconnection set up procedure such as Q. 2931, for example.

(3) When the connection set up address corresponding to the callterminating side terminal ID does not exist in the ARP table of the calloriginating side mobile terminal 201, the connection set up addressresolution operation is executed and the operation returns to the above(1).

Here, the connection set up address registration/resolution function canbe provided in the MSR. In such a configuration, it is possible to playa role of the location address registration function in the conventionalmobile communication. This connection set up addressregistration/resolution function is a function for registering andresolving the terminal ID and the connection set up address at least,and may be able to register and resolve the correspondence between theterminal ID and the IP address at the same time. Here, the connectionset up address comprises Network Prefix in an upper portion and theterminal ID in a lower portion.

In the above, an exemplary case of resolving the connection set upaddress first and then carrying out the IP address resolution operationafter the connection set up has been described, but it is also possibleto use a method in which the connection set up address is resolvedaccording to the need and the connection is set up after the IP addressresolution operation is executed. Also, in the case of carrying out theconnection set up address registration/resolution function and the IPaddress registration/resolution function simultaneously, there is noneed to carry out the IP address resolution operation and the connectionset up address resolution operation separately.

Next, the operation procedure in the case where the mobile terminal 201carries out the communication with the mobile terminal within thedifferent subnet will be described. As described below, the operationprocedure can use a method for utilizing the default VC network and amethod for utilizing the dedicated VC network, and it is preferable tochange which one of these methods is to be selected according to theapplication. The former method can be applied to the UBR and ABRservices of the ATM, while the latter method can be applied to the CBR,VBR and ABR services of the ATM.

When the mobile terminal exists at a location over subnets, the MSR 221cannot call that mobile terminal or make the call termination to thatmobile terminal because the location movement management for that mobileterminal is not carried out and therefore the location of that mobileterminal is not comprehended. In such a case, there is a need to carryout the location/address resolution of the mobile terminal indicating inwhich MSR the mobile terminal is existing. As a method for thislocation/address resolution, the following methods are available.

(1) A method for carrying out the location registration message exchange(TRAP type):

This is a method in which the location registration information isexchanged between the MSR 221 and the other MSR when there is a movingover subnets. Here, it is possible to carry out this locationregistration information exchange regardless of whether thecommunication is carried out or not, but it is preferable to use amethod in which the registration is carried out by selecting only thelocation registration information related to the other mobile terminalwith which the mobile terminal under its own location movementmanagement is communicating, because the table size becomes large andthere is a possibility for the amount of messages between the MSRs tobecomes enormous. Namely, when there is a moving over subnets, the MSRnotifies this moving to the other MSR.

Upon receiving the location registration message from the other MSR, theMSR recognizes whether the terminal corresponding to that message is theterminal within its own subnet and the terminal which is carrying outthe communication with the server and the like or not by referring tothe table, and when it is the terminal in communication, its locationinformation is updated. Here, in conjunction with the locationregistration updating, if the IP address change or the connection set upaddress change is also made, it is possible to notify this fact to therelated mobile terminal, or it is possible to carry out the conversionfrom the old IP address to the new IP address at the MSR. It is alsopossible to carry out the location registration message exchangedirectly between the mobile terminal in communication and the MSR. Insuch a case, in the Mobile IP like expression, it implies that the calloriginating side mobile terminal becomes HA.

(2) A method using the location/address resolution protocol (GET-SETtype):

The MSR 221 checks the current location of the mobile terminal using thelocation address resolution protocol with respect to the other MSR.Namely, the mobile terminal 201 transmits to the MSR 221 thelocation/address resolution request for obtaining the IP address and/orthe ATM address corresponding to the call terminating side terminal IDin order to communicate with the mobile terminal located in the othersubnet.

Upon receiving this location/address resolution request, the MSR 221checks whether the mobile terminal recognized by the terminal IDcontained in that location/address resolution request exists under itsown location movement management, and when the call terminating sidemobile terminal exists under its own location movement management, thecall termination to that call terminating side mobile terminal isexecuted.

When the call terminating side mobile terminal does not exist under itsown location movement management and under the location movementmanagement of which MSR this mobile terminal exists is uncertain, theserver function for managing the correspondence between the terminal IDof the mobile terminal in communication and the MSR under whose locationmovement management this mobile terminal exists is provided at thegateway and the like, and the location of the MSR corresponding to thecall terminating side ID is comprehended by making an access to thatserver. Then, the following operation is carried out.

Even when the call terminating side mobile terminal does not exist underits own location movement management, if the location information (theIP address or the connection set up address of the MSR in which thatcall terminating side mobile terminal exists) corresponding to that callterminating side terminal ID is comprehended by the exchange of thelocation registration information between the MSRs or by the access tothe above described server, that MSR is called and the call terminationconnection is requested, while the resolution of the IP address or theconnection set up address corresponding to the call terminating sideterminal ID is also requested.

Even when the call terminating side mobile terminal does not exist underits own location movement management, if the location information (theIP address or the connection set up address of that call terminatingside mobile terminal) corresponding to that call terminating sideterminal ID is comprehended by the exchange of the location registrationinformation between the MSRs or by the access to the above describedserver, that call terminating side mobile terminal is directly calledand the call termination connection operation is carried out.

Here, in the above described algorithm, the case of carrying out thecall termination connection operation has been described, but it is alsopossible to use a method in which only the location check operation iscarried out here, and the subsequently call termination connection iscarried out by the address resolution method in which the default VC(PVC) network is used and the framework of the conventional RARP ispartially expanded as described above.

Also, when it does not exists under the location movement management, itis possible to inquire the other MSR 221 to obtain the IP address or theconnection set up address of the desired mobile terminal and register itinto a correspondence table for the terminal ID and the IP address orthe connection set up address of the call terminating side mobileterminal, with respect to the MSR 220 in which that terminal exists.

Similarly, when the mobile terminal 201 makes an access to the serverand the like within Internet 224 (the global IP network), the private IPaddress is temporarily allocated by the DHCP server function provided atthe MSR 221, and the service is provided by making an access to thegateway using this allocated private IP address, converting this privateIP address into the global IP address by the address conversion (NAT)function of the gateway, and making an access to the WWW server and thelike within the global IP network using this converted global IPaddress.

In this case, when a unit of the DHCP allocation/release and a unit ofthe address conversion by the NAT are different and the mobile terminal201 moves from the area of the MSR 221 to the area of the MSR 220, thereis a need to change the correspondence between the private IP addressand the global IP address in the NAT table in conjunction with thatmoving.

Also, when the private IP address is released in conjunction with themoving of the mobile terminal 201, there is a need to cancel thatprivate IP address in the NAT table by notifying either the timer or thefact that the IP address is released to the device that has the NATfunction. In addition, when the private IP address is allocated inconjunction with the moving of the mobile terminal 201, there is a needto register that private IP address in the NAT table by notifying thefact that IP address is allocated to the device that has the NATfunction.

Similarly, for the connection set up between the mobile terminal 201 andthe MSR 220 or 221, in conjunction with the moving of the mobileterminal, there is also a need to release the connection set up betweenthe mobile terminal 201 and the MSR 220 at which the mobile terminal 201is located before the moving and set up a connection to the MSR 221 atwhich the mobile terminal 201 is located after the moving.

When the area in which the NAT function is provided and the area inwhich the DHCP function is provided coincides, the above describedoperation to update the NAT table in conjunction with the moving becomesunnecessary within the area in which the NAT function is provided, it isonly necessary to carry out the registration/cancallation operation inconjunction with the moving into/out of the NAT provided area.

If the DHCP server provided in the MSR 221 has a function fortemporarily allocating the global IP address, it is also possible tomake an access to the server within Internet 224 without carrying outthe NAT conversion at the gateway 223.

Besides that, if the DHCP server function for carrying out the IPaddress allocation/release is provided in the gateway 223, it ispossible for the mobile terminal 201 to carry out the connection set upwith respect to the gateway 223 so that the private IP address istemporarily issued and converted into the global IP address by theaddress conversion (NAT, etc.) function of the gateway 223 and an accessto the server within Internet 224 can be made by using this convertedglobal IP address. In this case, the NAT table carries out theregistration/cancellation in conjunction with the moving into/out of theNAT provided area.

Also, in the configuration in which the DHCP server function forcarrying out the IP address allocation/release is provided in thegateway 223, when the mobile terminal obtains the global IP address asthe IP address to be allocated temporarily after carrying out theconnection set up with respect to the gateway 223, it is possible tomake an access to the server within Internet 224 directly withoutcarrying out the conversion by the address conversion (NAT, etc.)function at the gateway 223.

Note that the method of connection set up described above may be carriedout by using the fixed dial number, the mobile dial number, or thedifferent number system such as ATM address. In addition, the connectioncan be made by using things like a name address or the Personal IDnumber. It is also possible to allocate the connection that is set up inadvance by making selection. In the above described example, thedatalink layer level exchange is carried out by the ATM but the presentinvention is not limited to the case of using the ATM alone.

Here, when the access to the global IP network is made and the mobileterminal within the private IP network moves over subnets, it ispossible to carry out the communication without influencing the serverand the like within the global IP network at all by carrying out thelocation registration of the mobile terminal at the gateway.

Next, with reference to FIGS. 52G and 52H, the concrete exemplaryoperation for the moving detection and the Mobile IP informationexchange in the case where the FA function is provided at the mobileterminal as shown in FIG. 53 will be described.

FIG. 52G shows a method in which the subnet ID is notified from theradio base station or the MSR, and FIG. 52H shows a method in which theradio base station constitutes a single subnet and the moving isdetected by detecting that the base station ID is different or that thereceived signal strength degraded.

In such a case, when the radio base station does not constitute a singlesubnet, as is the case when the MSR constitutes a single subnet, thewasteful registration and IP address allocation request will be carriedout. Consequently, in the case where the FA function is provided in themobile terminal, it is preferable to notify the subnet ID (subnet mask)information.

As described above, the mobile terminal 201 can realize the handoff byusing various handoff methods, and it is possible to change the handoffcontrol scheme to be used according to the protocol and applicationoperating on the upper level layer. For example, when the protocol andapplication operating on the upper level layer are such protocol andapplication for which the moving while maintaining the session ispreferable, the mobile terminal 201 carries out the handoff by using thevirtual subnet scheme or the Mobile IP so as to continue the IPcommunication, whereas when the protocol and application operating onthe upper level layer are such protocol and application for which thedisconnection of the session is not a problem, the mobile terminal 201operates to resume the IP communication by having a new IP addressallocated at the DHCP server at the visited site.

The functional arrangement of FIG. 49 comprises the mobile terminal 201,the radio base stations 202, 203, 210 and 211, the MSRs 220 and 221, thegateway 223, Internet 224, the home network 228 and a router 229 of thehome network 228, similarly as FIG. 47. The mobile terminal 201 has thelocation movement management (MM1 or MM2) function for the MSR, thenetwork layer address allocation/release (such as DHCP client) function,the call control (CC) function, the radio management (RT) function, anda Mobile IP function required for the terminal when the FA is located atthe network side. Each of the radio base stations 202, 203, 210 and 211has the location movement management (MM) function, the call control(CC) function, and the radio management (RT) function at least. The MSRhas the location movement management (MM) function, the network layeraddress allocation/release (such as DHCP server) function, the callcontrol (CC) function, the switch control (SWC) function, and thecut-through path set up/release (such as FANP) function, without havingany function related to the Mobile IP. Here, the DHCP server describedabove carries out the message exchange with the DHCP client, so as tocarry out the private IP address allocation.

Also, the gateway 223 has the address conversion (NAT) function, theforeign agent (FA) function for global network, the location movementmanagement (MM) function, the call control (CC) function, the switchcontrol (SWC) function, and the cut-through path set up/release (such asFANP) function. The MSR has the network layer address allocation/release(such as DHCP server) function in addition to the functions provided inthe gateway 223, so that the MSRs 220 and 221 can be directly connectedto Internet 224. This network layer address allocation/release (such asDHCP server) function provided in the MSR 220 and 221 carries out theallocation/release of the private IP address, while the foreign agent(FA) function is the FA for global network which has the global IPaddress.

In the case of FIG. 49, when the mobile terminal 201 makes an access tothe server and the like within the private IP network, the private IPnetwork Is provided between the MSRs 220 and 221, and the routing by theexchange at the datalink layer level is to be carried out between theMSR 220 and the radio base stations 202 and 203, between the MSR 221 andthe radio base stations 210 and 211, and between the radio base stations202, 203, 210 and 211 and the mobile terminal 201 (where the MSR has thegateway function). Also, when there is a call termination at the mobileterminal 201 from the IP terminal 225 within the global IP network, therouting by the exchange at the datalink layer level is carried out fromthe MSRs 220 and 221 (where the MSR has the gateway function).

Also, when the mobile terminal 201 makes an access to the server withinthe global IP network, the access can be made by using the routingmethod of either the form 1 or the form 2 described above.

Each of the MSRs 220 and 221 shown in FIG. 49 constitutes a singlesubnet, and has a configuration using the DHCP server function for theprivate network, the foreign agent (FA) function for the global network,and the address conversion (NAT) function, so that the FA function, theDHCP function, and the NAT function are provided at the same location.In the above described example, the datalink layer level exchange iscarried out by the ATM but the present invention is not limited to thecase of using the ATM alone.

Next, the method of access to the private IP network will be described.Basically, it is possible to use the same mechanism as in FIG. 46.

The FA address is obtained from the MSR, and when it is desired to makea global access, the communication is carried out by using this FAaddress. The call termination connection to the mobile terminal 201 canbe realized by the cooperative operation of the conventional Mobile IPand the location movement management function. The concrete operation isas shown in FIG. 51. As shown in FIG. 51, it is necessary to provide afunction for detecting the IP packet reception, calling the mobileterminal, resolving its location address, and carrying out theconnection set up according to its QOS requirement. Although notspecific to FIG. 49, the mobile terminal 201 has a configuration capableof changing the operation as to whether or not to set the Mobile IPoperation active according to the need or according to the application,in such a manner that, when it is desired to make a global access, themobile terminal 201 functions to carry out the Mobile IP operation byusing the FA address, and in the case of making a private access, theprivate IP address is obtained from the DHCP server and the access ismade without carrying out the Mobile IP operation.

Next, with reference to FIGS. 52A to 52F, the concrete exemplaryoperations for the moving detection and the Mobile IP informationexchange in the case where the FA function is provided at the networkside as shown in FIG. 49 will be described.

FIG. 52A shows a method in which the downlink message of the Mobile IPis received by utilizing the broadcast channel (BCCH), the calltermination control channel (PCH), and the downlink common controlchannel such as SCCH, and the uplink message of the Mobile IP istransmitted by utilizing the random access channel (RACH), the uplinkcommon control channel such as SCCH and USCCH or the individual controlchannel (FACCH, SACCH, USACCH, UFACCH). This is a method in which theregistration is carried out in such an order that the Mobile IP messageis transmitted in a form of inserting it into the above described radiolink control channel, the Agent Advertisement is received at the ICMPlevel by taking the Mobile IP message out, and the Registration messageis immediately transmitted according to the fact that the FA address isdifferent. The subsequent operation is as shown in FIG. 51.

FIG. 52B shows a method in which the subnet ID is periodicallytransmitted by containing it in the notification information of theradio link, where the subnet ID coincides with the FA address. FIG. 52Cshows a method in which the subnet ID is periodically transmitted bycontaining it in the notification information of the radio link, wherethe Registration is carried out in such an order that the moving isdetected by the fact that the subnet ID is different, the notificationis urged by the Care-of-address solicitation, and the Care-of-address isobtained by looking at the notification information (Agent Advertisementor FA address) within the BCCH for that packet communication.

The advantage of this method is that there is no need to refer to theBCCH for packet communication unless it is necessary, and when it isnecessary, there is no need to assemble the Agent advertisement message.

Also, FIG. 52D and FIG. 52E show methods in which the subnet ID isperiodically transmitted by containing it in the notificationinformation of the radio link level. The methods of FIG. 52A to FIG. 52Care basically for the cases where BCCH for packet (IP) communication isto be newly defined and operated or the existing BCCH has sufficientreservation bits, but the methods of FIGS. 52D and 52E can be used forthe cases where it is difficult to newly define BCCH for packet (IP)communication as the notification information (and there is not muchreservation bit in the existing BCCH).

Also, FIG. 52F shows a method In which the solicitation is made bydetecting the fact that the received signal strength degraded. Here,after the solicitation, the operation in the procedure of the methods ofFIGS. 52A and 52B is shown, but it is also possible to use the operationin the procedure after the solicitation of the method of FIG. 52E.

Next, the configuration of the Internet access sub-system is shown inFIG. 53.

In FIG. 53, N pieces of the class B addresses of IPv4 are allocated asthe IP addresses to the gateway (in the following, it is assumed thatN=4 for the sake of definiteness). As shown in FIG. 53, the connectionswith the other networks such as Internet and ODN (Open Digital Network)are made through this gateway.

FIG. 53 shows an exemplary case in which the addresses 133.196 to133.199 (for the case of N=4) in upper 16 bits are allocated as thenetwork address for representing this Internet access sub-system as awhole. In this case, for the hosts within this system, the addresses133.169.0.0 to 133.169.255.255 can be set up. In practice, the addresseswith all 0 or all 1 host section are utilized for the special purposesand cannot be utilized as the host address, so that up to(2¹⁶−2)×4=65534×4=262136 terminals can be set up. This implies that thenumber of connectable hosts is at most 262136, so that it lacks theexpandability. For this reason, in the Internet access sub-system shownin FIG. 53, it is important to make it possible for those hosts whoseutilization times do not overlap with each other to be able to use thesame address by using the DHCP for allocating the IP addressestemporarily whenever necessary. In this manner, it is possible toincrease the number of hosts that can be accommodated, and to deal withthe moving of the hosts.

Also, the configuration of FIG. 53 uses the DSA (Dynamic SubnetAssignment) server function in order to improve the flexibility of thesystem configuration and the performance of the IP addressallocation/release processing. In addition, by carrying out the IPaddress allocation/release hierarchically by using the DSA serverfunction and the DHCP server function together in such a manner that thesubnet address is allocated to the MSR by providing the DSA serverfunction in the gateway while the IP address is allocated to the host byproviding the DHCP server function in the MSR, it becomes possible toutilize the IP addresses more effectively.

The DSA carries out the allocation/release of the subnet addressdynamically according to the need, and by using the DSA, there is anadvantage in that it is possible to change the subnet address allocationflexibly according to the traffic state of the system after the systemis introduced, in such a manner that many subnet addresses are allocatedto the service area with heavy traffic such as business quarters whileonly a small number of subnet addresses are allocated to the servicearea at which Internet accesses occur less frequently.

Also, unlike the case in which the gateway allocates the IP addresses toall the hosts, by realizing the IP address allocation/release processinghierarchically, it is possible to distribute the processing andtherefore there is a merit in that it can lead to the lowering of theload on the DHCP server.

Note that the system of FIG. 53 is in a configuration in which thefunctional arrangements of FIG. 47 and FIG. 50 as described above aremerged together, which includes the case in which the mobile terminalhas the FA function and the case in which the MSR has the FA function.In addition, it is also possible to use a configuration as shown in FIG.54 in which the VIP function rather than the Mobile IP function isprovided in the MSR so that the VIP addresses are allocated by the DHCPserver provided in the MSR.

On the other hand, in Internet, the routing is carried out according tothe IP address. Thus a plurality of subnets are defined within onenetwork, and the hop-by-hop routing is carried out up to that subnet,while the routing according to the datalink address (MAC address) iscarried out within the subnet. For this reason, even for the routing inthe radio Internet system as shown in FIG. 53 and FIG. 54, it is alsopossible to use a method as shown in FIG. 55 in which the upper 4 bitsof the host section are allocated as the network address (subnet masksare 225.225.240.0 (FF.FF.F0.00)) to the MSR, the next 4 bits subsequentto the network section containing the subnet section are utilized as theradio base station ID, and the subsequent 8 bits are utilized as thehost ID of a host to be connected to each radio base station.

With this configuration, it is possible to carry out the routing withinthe mobile communication system in the framework of the IP routingrather than the frame work of the routing in the conventional mobilecommunication network. In this example, it is possible to accommodate atmost 16 sets of the radio base stations for one MSR, so that it ispossible to accommodate at most 256 sets of the hosts at each radio basestation.

Next, in the system shown in FIG. 53 and FIG. 54, (1) the operation at atime of making an access from the mobile terminal to the mail server,(2) the operation at a time of making an access from the mobile terminalto the WWW server, and (3) the operation at a time of making an accessfrom the mobile terminal to a remote host which is located beyond theglobal Internet network, will be described.

(1) Mail access operation procedure:

FIG. 56 shows the case of the mail transfer operation, which will now bedescribed according to this FIG. 56. First, when the user transmits amail, the mail reaches to the nearest mail server. Then, it istransferred to the correspondent through many servers. The SMTP (SimpleMail Transfer Protocol) is a protocol in which the mail message isexchanged between the transmitting terminal and the server and betweenthe servers. Using this SMTP, the mail message is transferred throughInternet, but the destination mobile terminal is usually not implementedwith the SMTP server function so that it takes out the message from thenearest server by utilizing a protocol called POP (Post OfficeProtocol). In other words, the mobile terminal receives the mail serviceby using the SMTP at a time of transmitting mail, and using the POP at atime of receiving mail.

As shown in FIG. 56, even when the mobile terminal moves between theradio base stations, the handoff control function is supported by theMSR so that it is possible to realize the mail access in the same formas the usual mail access in the fixed network. Also, FIG. 57 shows themail transfer operation procedure. The operation in the case where auser transmits or receives mail will now be described according to thisFIG. 57. First the radio link negotiation is made between the radio basestation and the mobile terminal so as to establish the radio link. Then,the mobile terminal is allocated with the IP address by the DHCPprovided in the MSR. Then, when the IP address is obtained, the mobileterminal makes an access to the mail server by using the SMTP in thecase of mail transmission or by using the POP in the case of mailreception. Then, when the mail transmission or reception is finished,the IP address release operation of the DHCP is carried out between themobile terminal and the MSr, and the disconnection of the radio link iscarried out between the mobile terminal and the radio base station.

(2) WWW server access operation procedure:

The WWW (World Wide Web) is a mechanism in which the information datawithin servers which are distributed over Internet are related in a formof spider's web and made to be retrievable. In the WWW, the informationof anonymous FTP, Net News and Gopher can be utilized directly. Also,the WWW is basically realized by communications between servers andclients and highly reliable communications are realized by using theprotocol called HTTP (Hyper Text Transfer Protocol) on the TCP protocol(TELNET).

FIG. 58 shows a communication system configuration and the FIG. 59 showsthe WWW server access operation procedure. The mobile terminal of thecommunication system of FIG. 58 has a WWW browser mounted thereon. TheWWW proxy server is a server which makes request on behalf of the otherclients, which plays both the roles of the server and the client. ThisWWW proxy server has a cache function, a firewall function, a codeconversion function, and a multi-protocol function. Also, the gateway isa server for relaying the other servers.

In the following, the operation in the case where the mobile terminalobtains information from the HTTP server using the WWW browser will bedescribed.

First, the mobile terminal makes a negotiation of the radio link withthe radio base station, so as to establish the radio link. Then, the IPaddress is obtained by using the DHCP protocol between the mobileterminal and the MSR. Then, when the IP address is obtained, the TCPconnections are set up in an order of: mobile terminal→WWW proxy server,gateway GW1→gateway GW2→HTTP server, so that the TCP connection up tothe WWW server at which the URL (Uniform Resource Locator) of interestexists is established. Then, when the user tries to acquire theinformation on the WWW browser, a Request message in the HTTP protocolis transmitted through the four connections as indicated in FIG. 59,from the mobile terminal toward the HTTP server. Upon receiving this,the HTTP server transmits the information requested from the user usinga Response message in the HTTP protocol. Then, the WWW serverdisconnects the TCP connection with the mobile terminal (the case of (A)shown in FIG. 59).

In the WWW system, the server and the client are connected only whilethe data request using URL is issued and the requested data areacquired, While the user reads the acquired data on the WWW browser, theTCP connection is disconnected.

Now, when the data to be requested by the user next are already cachedin the WWW proxy server, the connection set up is carried out only up tothe WWW proxy server and the Request and Response messages in the HTTPprotocol are exchanged between the mobile terminal and the WWW proxyserver, as shown in the case (b) of FIG. 59. Namely, the information(resource) once transferred from Internet is stored in a cache at theWWW proxy server and when the same resource in the cache is requested,the resource stored in the cache is given to the client rather thangoing up to Internet to obtain the same thing. When the browsing at themobile terminal is finished, the IP address release is carried outbetween the mobile terminal and the MSR, and the disconnection of theradio link is carried out between the mobile terminal and the radio basestation.

(3) Internet connection operation procedure:

Next, the procedure for transmitting data from the mobile terminal to aremote host (RS) through Internet will be described. FIG. 60 shows aconnection configuration in this case. The mobile terminal transmits theIP datagram with respect to the remote host on Internet through theradio base station, the MSR, and the gateway. At this point, theconversion such as that of the media coding scheme is carried out by themedia conversion server (media server) connected to the MSR according tothe need. The data transmission procedure in this case will now bedescribed with reference to FIG. 61.

First, the establishing of the radio link between the mobile terminaland the radio base station, and the acquisition of the IP address of themobile terminal are carried out.

Then, the information related to the media communication scheme, that isthe information on the coding scheme of the media, the transportprotocol to be used, etc., is exchanged between the mobile terminal andthe connection target remote host, so as to recognize the mediacommunication scheme to be used on both sides. When the mediacommunication scheme to be used is different at the mobile terminal andthe remote host as a result of the exchange of this information relatedto the media communication scheme, the mobile terminal transmits themedia data through the media conversion server. Namely, the mobileterminal transmits the IP datagram with the destination addressinformation of the remote host attached thereto to the media conversionserver. At the media conversion server, the IP datagram is assembledonce and the media conversion processing is applied, and then it istransmitted to the remote host as the IP datagram again. At this point,the transport protocol conversion processing is also carried out ifnecessary. On the other hand, when the media communication scheme is thesame at the mobile terminal and the remote host, the mobile terminaltransmits the IP datagram directly to the remote host without using themedia conversion server.

In the above described procedure, the media conversion server has beendescribed as a specific server connected to the MSR, but it is alsopossible to use a method in which the media conversion server that hasthe necessary conversion capability is searched out and then utilized ateach occasion. This method can be realized by obtaining the informationon the available media conversion servers using the inquiry proceduresuch as SLP (Service Location Protocol), for example, at a timingindicated by *1 in FIG. 61. It is also possible to use a method in whichaddresses of various servers are notified from the radio base stationinstead of using such an inquiry procedure.

As described, the Internet type mobile access technique has beenassociated with the problem of redundancy of the route and the problemthat the handoff control associated with the moving is very timeconsuming so that it has been difficult to realize the real timecommunication such as Internet telephone under the mobile Internetenvironment, but by using the mobile supporting router device of thepresent invention, it becomes possible to carry out the handoff controlmuch faster than the handoff in the conventional Internet type system.

Also, by providing the router local location movement managementfunction in this high speed router device, it becomes possible toprovide the mobile supporting router device which is capable of reducingthe delay time and the route redundancy compared with the conventionalmobile access technique such as Mobile IP.

It is to be noted that, besides those already mentioned above, manymodifications and variations of the above embodiments may be madewithout departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

1. A router device, comprising: at least one first interface connectedwith a plurality of radio base stations, each radio base stationconfigured to accommodate at least one mobile terminal; at least onesecond interface connected with a network; an information exchangingunit configured to exchange a routing protocol on a network layer,through the second interface; a memory unit configured to storeinformation regarding a routing on the network layer based on therouting protocol exchanged by the information exchanging unit; atransfer unit configured to transfer datagram through the firstinterface according to the information regarding the routing on thenetwork layer stored in the memory unit; a moving detection unitconfigured to detect a moving of the mobile terminal among the radiobase stations; and an information updating unit configured to update theinformation regarding the routing on the network layer stored in thememory unit when the moving of the mobile terminal is detected by themoving detection unit, wherein the transfer unit transfers the datagramthrough the first interface according to another information regarding aswitching on a lower layer of the network layer for enabling datagramtransfer along the routing on the network layer when a prescribedcondition for the switching on the lower layer is satisfied.
 2. Therouter device of claim 1, further comprising: another memory unit forstoring said another information regarding the switching on the lowerlayer of the network layer, wherein the information updating unit alsoupdates said another information regarding the switching on the lowerlayer of the network layer stored in said another memory unit when themoving of the mobile terminal is detected by the moving detection unit.3. The router device of claim 1, further comprising: another memory unitfor storing a correspondence between a first virtual connection forconnecting the first interface and a radio base station of a currentlylocated site of the mobile terminal and a second virtual connectiondifferent from the first virtual connection, as said another informationregarding the switching on the lower layer of the network layer; whereinwhen the moving of the mobile terminal corresponding to the firstvirtual connection is detected by the moving detection unit, theinformation updating unit also updates said another informationregarding the switching on the lower layer of the network layer storedin said another memory unit, by obtaining a third virtual connection forconnecting the first interface and a radio base station of a visitedsite of the mobile terminal and storing a correspondence between thethird virtual connection and the second virtual connection in saidanother memory unit, while updating the information regarding therouting on the network layer by storing a network layer address of themobile terminal after the moving and the third virtual connection in thememory unit.
 4. The router device of claim 1, further comprising:another memory unit for storing a correspondence between a first virtualconnection for connecting the first interface and a radio base stationof a currently located site of the mobile terminal and a second virtualconnection different from the first virtual connection, as said anotherinformation regarding the switching on the lower layer of the networklayer; wherein when the moving of the mobile terminal corresponding tothe first virtual connection is detected by the moving detection unit,the information updating unit updates the information regarding therouting on the network layer by identifying a correspondence between anetwork layer address of the mobile terminal and a third virtualconnection for connecting the first interface and a radio base stationof a visited site of the mobile terminal according to message exchangewith the mobile terminal or the radio base station of the visited siteof the mobile terminal, and by storing the identified correspondence inthe memory unit, while also updating said another information regardingthe switching on the lower layer of the network layer stored in saidanother memory unit by storing a correspondence between the thirdvirtual connection and the second virtual connection in said anothermemory unit.
 5. The router device of claim 1, further comprising: aswitching unit for switching transfer of the datagram by the transferunit between datagram transfer according to the information regardingthe routing on the network layer and datagram transfer according to saidanother information regarding the switching on the lower layer of thenetwork layer.